Glass with high surface strength

ABSTRACT

Embodiments of alkali aluminosilicate glass articles that may be chemically strengthened to achieve a maximum surface compressive stress that exceeds compressive stresses that have been achieved in similar glasses are disclosed. In one or more embodiments, the fictive temperature of these glass articles may be equal to the 1011 poise (P) viscosity temperature of the glass article. In some embodiments, the strengthened alkali aluminosilicate glass articles described herein may exhibit a maximum compressive stress of at least about 400 MPa, 800 MPa, 930 MPa or 1050 MPa. In some embodiments, the strengthened alkali aluminosilicate glass articles described herein may exhibit a compressive stress layer extending to a depth of layer of at least about 40 μm (in samples having a thickness of 1 mm). In still other embodiments, these strengthened alkali aluminosilicate glass articles exhibit a parabolic or near-parabolic tensile stress profile in the central region of the glass articles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application and claims the benefit ofpriority under 35 U.S.C. § 120 of U.S. application Ser. No. 15/191,961filed on Jun. 24, 2016, which in turn, claims the benefit of priorityunder 35 U.S.C. § 119 of U.S. Provisional Application Ser. No.62/266,417 filed on Dec. 11, 2015 and U.S. Provisional Application Ser.No. 62/184,933 filed on Jun. 26, 2015, the contents of each of which arerelied upon and incorporated herein by reference in their entireties.

BACKGROUND

The disclosure relates to a chemically strengthened glass article. Moreparticularly, the disclosure relates to chemically strengthened glassarticles comprising a surface layer having a high compressive stress.

Glass articles are widely used in electronic devices as cover plates orwindows for portable or mobile electronic communication andentertainment devices, such as cellular phones, smart phones, tablets,video players, information terminal (IT) devices, laptop computers andthe like, as well as in other applications. As glass articles becomemore widely used, it has become more important to develop strengthenedglass articles having improved survivability, especially when subjectedto tensile stresses and/or relatively deep flaws caused by contact withhard and/or sharp surfaces.

SUMMARY

The present disclosure provides alkali aluminosilicate glass articlesthat may be chemically strengthened by an ion exchange process to imparta compressive stress on surface portions thereof that exhibit a maximumsurface compressive stress that exceeds the compressive stresses thathave been achieved in similar glasses. For example, in one or moreembodiments, the glasses described herein may be ion exchanged toachieve a surface compressive stress of at least about 400 MPa, at leastabout 800 MPa, at least about 930 MPa, or at least about 1050 MPa. Inone or more embodiments, the compressive stress layer extends from asurface to various depths of layer (DOL). For example, DOL may be about25 μm or less. In other embodiments, the alkali aluminosilicate glassarticles may be ion exchanged to achieve a deeper or thicker compressivelayer (e.g., at least about 40 μm). These DOL values may be exhibited inglass articles having a thickness of about 1 mm. In still otherembodiments, these glasses may be ion exchanged such that the resultingglass article includes a central region extending from the DOL to adepth into the glass article that includes a tensile stress having aparabolic or near-parabolic profile. In one or more embodiments, thealkali aluminosilicate glass may exhibit a tensile region extending fromthe DOL into the glass article. The tensile region of one or moreembodiments may exhibit a maximum tensile stress of less than about 20MPa. The tensile region of one or more embodiments may exhibit a maximumtensile stress of greater than about 40 MPa (e.g., about 45 MPa orgreater, about 50 MPa or greater, about 60 MPa or greater, about 70 MPaor greater, about 75 MPa or greater, about 80 MPa or greater, or about85 MPa or greater).

In one or more embodiments, the alkali aluminosilicate glass articlesmay comprise a fictive temperature is equal to the 10¹¹ poise (P)viscosity temperature of the glass article. In one or more embodiments,the alkali aluminosilicate glass article comprises a zircon breakdowntemperature of less than about 35 kPoise. In one or more embodiments,the alkali aluminosilicate glass article comprises a liquidus viscosityof at least 200 kPoise.

A second aspect of this disclosure pertains to an alkali aluminosilicateglass article comprising a certain composition. In one or moreembodiments, such articles can be chemically strengthened to achieve theattributes described herein. In one or more embodiments, the alkalialuminosilicate glass article comprises at least about 58 mol % SiO₂,from about 0.5 mol % to about 3 mol % P₂O₅, at least about 11 mol %Al₂O₃, Na₂O and Li₂O. In one or more embodiments, the alkalialuminosilicate glass article comprises from about 58 mol % to about 65mol % SiO₂; from about 11 mol % to about 19 mol % Al₂O₃; from about 6mol % to about 18 mol % Na₂O; from 0 mol % to about 6 mol % MgO; andfrom 0 mol % to about 6 mol % ZnO.

In one or more embodiments, the alkali aluminosilicate glass exhibits acompositional ratio of the amount of Li₂O (mol %) to the amount of Na₂O(mol %) (i.e., Li₂O/Na₂O) that is less than 1.0. In one or moreembodiments, the alkali aluminosilicate glass article is free of B₂O₃.In one or more embodiments, the alkali aluminosilicate glass articlecomprises a ratio R₂O (mol %)/Al₂O₃ (mol %) that is less than 2, whereR₂O=Li₂O+Na₂O. In one or more embodiments, the alkali aluminosilicateglass article comprises a total amount of SiO₂ and P₂O₅ that is greaterthan 65 mol % and less than 67 mol % (65 mol %<SiO₂ (mol %)+P₂O₅ (mol%)<67 mol %). In some instances, the alkali aluminosilicate glassarticle comprises a relationship R₂O (mol %)+R′O (mol %)−Al₂O₃ (mol%)+P₂O₅ (mol %) that is greater than about −3 mol %, wherein R₂O=thetotal amount of Li₂O and Na₂O present in the alkali aluminosilicateglass article and WO is a total amount of divalent metal oxides presentin the alkali aluminosilicate glass article. In some instances, thealkali aluminosilicate glass article comprises P₂O₅ in an amount in arange from about 0.5 mol % to about 2.8 mol %. In some other instances,the alkali aluminosilicate glass article comprises Li₂O in an amount upto about 10 mol % Li₂O.

In one or more embodiments, the alkali aluminosilicate glass articlesmay have a thickness in a range from about 0.05 mm to about 1.5 mm. Forexample, the thickness may be from about 0.1 mm to about 1.5, from about0.3 mm to about 1.2 mm, from about 0.4 mm to about 1.2 mm or from about0.5 mm to about 1.2 mm. In one or more embodiments, the alkalialuminosilicate glass articles may have a thickness of at least about 1mm and may exhibit a maximum compressive stress of at least about 930MPa at the surface. In one or more embodiments, the alkalialuminosilicate glass articles may have a thickness of at least about 1mm and may exhibit a maximum compressive stress of at least about 1050MPa at the surface. In one or more embodiments, the alkalialuminosilicate glass article may exhibit a bend radius of less thanabout 37 mm or less than about 35 mm, at a thickness of about 1 mm.

In one or more embodiments, the alkali aluminosilicate glass articlesdescribed herein may include a central region extending from the DOL toa depth equal to 0.5 times the thickness, and this central region may befree of K₂O.

A third aspect of the disclosure relates to an alkali aluminosilicateglass article having a thickness t, a compressive stress layer extendingfrom a surface of the alkali aluminosilicate glass to a DOL, and acentral region extending from the DOL, wherein the central region isunder a tensile stress, wherein DOL≤0.25t, and wherein the tensilestress is at least about 35 MPa. The alkali aluminosilicate glassarticle is free of B₂O₃ and, in some embodiments, K₂O, and comprises atleast 0.5 mol % P₂O₅, Na₂O and, Li₂O, wherein Li₂O (mol %)/Na₂O (mol%)<1. In some embodiments, alkali aluminosilicate glass article includesat least about 58 mol % SiO₂, from about 0.5 mol % to about 3 mol %P₂O₅, at least about 11 mol % Al₂O₃, Na₂O and, Li₂O, wherein the ratioof the amount of Li₂O (mol %) to Na₂O (mol %) (Li₂O/Na₂O) is less than1.0

A fourth aspect of the disclosure pertains to a transparent laminate.The transparent laminate comprises an alkali aluminosilicate glassarticle as described herein joined to a second article. The secondarticle may comprise a transparent substrate. A fifth aspect of thisdisclosure pertains to a consumer electronic device including one ormore embodiments of the alkali aluminosilicate glass articles describedherein, which may be chemically strengthened as described herein. In oneor more embodiments, the consumer electronic device comprises: ahousing; electrical components provided at least partially internal tothe housing, the electrical components including at least a controller,a memory, and a display, the display being provided at or adjacent to afront surface of the housing; and a cover article disposed at or overthe front surface of the housing and over the display, wherein the coverarticle comprises one or more embodiments of the alkali aluminosilicateglass article described herein.

A sixth aspect of the disclosure pertains to a method of making astrengthened alkali aluminosilicate glass article that comprises acompressive stress layer. In one or more embodiments, the methodcomprises generating a compressive stress in an alkali aluminosilicateglass article by ion exchanging the aluminosilicate glass article. Inone or more embodiments, the compressive stress layer extends from asurface of the alkali aluminosilicate glass article to a DOL. Thecompressive stress layer may comprise a maximum compressive stress ofabout 400 MPa or greater, about 800 MPa or greater or about 1050 MPa orgreater. In one or more embodiments, the DOL may be at least about 40μm. In one or more embodiments, ion exchanging the alkalialuminosilicate glass comprises immersing the alkali aluminosilicateglass in a molten salt bath. The molten salt bath can comprise NaNO₃,KNO₃ or both NaNO₃ and KNO₃. In one or more embodiments, the method mayinclude joining the ion exchanged alkali aluminosilicate glass to asubstrate to form a laminate structure. In one or more embodiments, themethod may include joining the ion exchanged alkali aluminosilicateglass to an electronic device housing.

These and other aspects, advantages, and salient features will becomeapparent from the following detailed description, the accompanyingdrawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a strengthened alkalialuminosilicate glass article according to one or more embodiments;

FIG. 2 is a schematic cross sectional view of a laminate comprising oneor more embodiments of the alkali aluminosilicate glass articlesdescribed herein; and

FIG. 3 is schematic, front plan view of a consumer electronic productincluding one or more embodiments of the alkali aluminosilicate glassarticles described herein; and

FIG. 4 is a schematic, prospective view of the consumer electronicproduct of FIG. 3.

DETAILED DESCRIPTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, it is understood that the group maycomprise, consist essentially of, or consist of any number of thoseelements recited, either individually or in combination with each other.Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, it is understood thatthe group may consist of any number of those elements recited, eitherindividually or in combination with each other. Unless otherwisespecified, a range of values, when recited, includes both the upper andlower limits of the range as well as any ranges therebetween. As usedherein, the indefinite articles “a,” “an,” and the correspondingdefinite article “the” mean “at least one” or “one or more,” unlessotherwise specified. It also is understood that the various featuresdisclosed in the specification and the drawings can be used in any andall combinations.

As used herein, the term “glass article” is used in its broadest senseto include any object made wholly or partly of glass. Unless otherwisespecified, all compositions of the glasses described herein areexpressed in terms of mole percent (mol %), and the constituents areprovided on an oxide basis. The compositions of all molten salt baths—aswell as any other ion exchange media—that are used for ion exchange areexpressed in weight percent (wt %). Coefficients of thermal expansion(CTE) are expressed in terms of parts per million (ppm)/° C. andrepresent a value measured over a temperature range from about 20° C. toabout 300° C., unless otherwise specified. High temperature (or liquid)coefficients of thermal expansion (high temperature CTE) are alsoexpressed in terms of part per million (ppm) per degree Celsius (ppm/°C.), and represent a value measured in the high temperature plateauregion of the instantaneous coefficient of thermal expansion (CTE) vs.temperature curve. The high temperature CTE measures the volume changeassociated with heating or cooling of the glass through thetransformation region.

Unless otherwise specified, all temperatures are expressed in terms ofdegrees Celsius (° C.). As used herein the term “softening point” refersto the temperature at which the viscosity of a glass is approximately10^(7.6) poise (P), the term “anneal point” refers to the temperature atwhich the viscosity of a glass is approximately 10^(13.2) poise, theterm “200 poise temperature (T^(200P))” refers to the temperature atwhich the viscosity of a glass is approximately 200 poise, the term“10¹¹ poise temperature” refers to the temperature at which theviscosity of a glass is approximately 10¹¹ poise, the term “35 kPtemperature (T^(35kP))” refers to the temperature at which the viscosityof a glass is approximately 35 kilopoise (kP), and the term “160 kPtemperature (T^(160kP))” refers to the temperature at which theviscosity of a glass is approximately 160 kP.

As used herein, the term “zircon breakdown temperature” or“T^(breakdown)” refers to the temperature at which zircon—which iscommonly used as a refractory material in glass processing andmanufacture—breaks down to form zirconia and silica, and the term“zircon breakdown viscosity” refers to the viscosity of the glass atT^(breakdown). The term “liquidus viscosity” refers to the viscosity ofa molten glass at the liquidus temperature, wherein the liquidustemperature refers to the temperature at which crystals first appear asa molten glass cools down from the melting temperature, or thetemperature at which the very last crystals melt away as temperature isincreased from room temperature. The term “35 kP temperature” or“T^(35kP)” refers to the temperature at which the glass or glass melthas a viscosity of 35,000 Poise (P), or 35 kiloPoise (kP).

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. Thus, a glass that is “substantially free ofK₂O” is one in which K₂O is not actively added or batched into theglass, but may be present in very small amounts as a contaminant.

As used herein, “maximum compressive stress” refers to the highestcompressive stress value measured within the compressive stress layer.In some embodiments, the maximum compressive stress is located at thesurface of the glass. In other embodiments, the maximum compressivestress may occur at a depth below the surface, giving the compressiveprofile the appearance of a “buried peak.” Compressive stress ismeasured by surface stress meter (FSM) using commercially availableinstruments such as the FSM-6000, manufactured by Orihara IndustrialCo., Ltd. (Japan). Surface stress measurements rely upon the accuratemeasurement of the stress optical coefficient (SOC), which is related tothe birefringence of the glass. SOC in turn is measured according to amodified version of Procedure C described in ASTM standard C770-98(2013), entitled “Standard Test Method for Measurement of GlassStress-Optical Coefficient,” the contents of which are incorporatedherein by reference in their entirety. The modification includes using aglass disc as the specimen with a thickness of 5 to 10 mm and a diameterof 12.7 mm, wherein the disc is isotropic and homogeneous and coredrilled with both faces polished and parallel. The modification alsoincludes calculating the maximum force, Fmax to be applied. The forceshould be sufficient to produce at least 20 MPa compression stress. Fmaxis calculated as follows:

Fmax=7.854*D*h

Where:

Fmax=Force in Newtons

D=the diameter of the disc

h=the thickness of the light path

For each force applied, the stress is computed as follows:

σ_(MPa)=8F/(π*D*h)

Where:

F=Force in Newtons

D=the diameter of the disc

h=the thickness of the light path

As used herein, DOL means the depth at which the stress in thechemically strengthened alkali aluminosilicate glass article describedherein changes from compressive to tensile. DOL may be measured by FSMor SCALP depending on the ion exchange treatment. Where the stress inthe glass article is generated by exchanging potassium ions into theglass article, FSM is used to measure DOL. Where the stress is generatedby exchanging sodium ions into the glass article, SCALP is used tomeasure DOL. Where the stress in the glass article is generated byexchanging both potassium and sodium ions into the glass, the DOL ismeasured by SCALP, since it is believed the exchange depth of sodiumindicates the DOL and the exchange depth of potassium ions indicates achange in the magnitude of the compressive stress (but not the change instress from compressive to tensile); the exchange depth of potassiumions in such glass articles is measured by FSM.

Referring to the drawings in general and to FIG. 1 in particular, itwill be understood that the illustrations are for the purpose ofdescribing particular embodiments and are not intended to limit thedisclosure or appended claims thereto. The drawings are not necessarilyto scale, and certain features and certain views of the drawings may beshown exaggerated in scale or in schematic in the interest of clarityand conciseness.

Described herein are alkali aluminosilicate glasses that may bechemically strengthened by an ion exchange process to impart a surfacecompressive stress that exceeds compressive stresses that have beenachieved in similar glasses. For example, when 1 mm thick coupons of theglasses described herein are ion exchanged in a molten potassium nitrateion exchange bath at 410° C. for 45 minutes, a maximum surfacecompressive stress exceeding about 1050 MPa, or, in some embodiments,exceeding about 1075 MPa, or, in still other embodiments, at least 1100MPa is obtained. The fictive temperature equal of these glasses is equalto the 10¹¹ P temperature of the glass.

In one or more embodiments, the alkali aluminosilicate glass articleshave a homogenous in microstructure (i.e., the glass is not phaseseparated). In one or more embodiments, the alkali aluminosilicate glassarticle is amorphous. As used herein, “amorphous” when used to describeglass article means substantially free of crystallites or crystallinephases (i.e., containing less than 1 vol % crystallites or crystallinephases).

The alkali aluminosilicate glass articles described herein are formedfrom glass compositions that are fusion formable. In one or moreembodiments, the glass composition may have a liquidus viscosity greaterthan about 200 kilopoise (kP) and, in some embodiments, having aliquidus viscosity of at least about 600 kP. In some embodiments, theseglass articles and compositions are compatible with a zircon isopipe:the viscosity at which the glass breaks down the zircon isopipe tocreate zirconia defects is less than 35 kP. Selected glass compositionswithin the composition ranges described herein may have a zirconbreakdown viscosity that is greater than 35 kP. In such instances, analumina isopipe may be used to fusion form these glass articles.

In one or more embodiments, the alkali aluminosilicate glass articlesmay include a glass composition that comprises at least 0.5 mol % P₂O₅,Na₂O and, optionally, Li₂O, where Li₂O (mol %)/Na₂O (mol %)<1. Inaddition, these glasses are free of B₂O₃ and K₂O. The alkalialuminosilicate glasses described herein may further include ZnO, MgO,and SnO₂.

In some embodiments, the alkali aluminosilicate glass article comprisesor consists essentially of at least about 58 mol % SiO₂, from about 0.5mol % to about 3 mol % P₂O₅, at least about 11 mol % Al₂O₃, Na₂O andLi₂O.

In one or more embodiments, the alkali aluminosilicate glass articlecomprises or consists essentially of from about 58 mol % to about 65 mol% SiO₂; from about 11 mol % to about 20 mol % Al₂O₃; from about 0.5 mol% to about 3 mol % P₂O₅; from about 6 mol % to about 18 mol % Na₂O; from0 mol % to about 6 mol % MgO; and from 0 mol % to about 6 mol % ZnO. Incertain embodiments, the glass comprises or consists essentially of fromabout 63 mol % to about 65 mol % SiO₂; from 11 mol % to about 19 mol %Al₂O₃; from about 1 mol % to about 3 mol % P₂O₅; from about 9 mol % toabout 20 mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0 mol %to about 6 mol % ZnO.

In one or more embodiments, the alkali aluminosilicate glass articlecomprises the ratio R₂O (mol %)/Al₂O₃ (mol %) that is less than about 2(e.g., less than about 1.8, less than about 1.6, less than about 1.5, orless than about 1.4), where R₂O=Li₂O+Na₂O.

In one or more embodiments, the alkali aluminosilicate glass articlecomprises the relationship where the total amount of SiO₂ and P₂O₅ thatis greater than 65 mol % and less than 67 mol % (i.e., 65 mol %<SiO₂(mol %)+P₂O₅ (mol %)<67 mol %). For example, the total amount of SiO₂and P₂O₅ may be in a range from about 65.1 mol % to about 67 mol %, fromabout 65.2 mol % to about 67 mol %, from about 65.3 mol % to about 67mol %, from about 65.4 mol % to about 67 mol %, from about 65.5 mol % toabout 67 mol %, from about 65.6 mol % to about 67 mol %, from about 65.7mol % to about 67 mol %, from about 65.8 mol % to about 67 mol %, fromabout 65.9 mol % to about 67 mol %, from about 66 mol % to about 67 mol%, from about 65 mol % to about 66.9 mol %, from about 65 mol % to about66.8 mol %, from about 65 mol % to about 66.7 mol %, from about 65 mol %to about 66.6 mol %, from about 65 mol % to about 66.5 mol %, from about65 mol % to about 66.4 mol %, from about 65 mol % to about 66.3 mol %,from about 65 mol % to about 66.2 mol %, from about 65 mol % to about66.1 mol %, or from about 65 mol % to about 66 mol %.

In one or more embodiments, the alkali aluminosilicate glass articlecomprises a relationship R₂O (mol %)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol%) that is greater than about −3 mol % (i.e., R₂O (mol %)+R′O (mol%)−Al₂O₃ (mol %)+P₂O₅ (mol %)>−3 mol %). In one or more embodiments, R₂Ois the total amount of Li₂O and Na₂O (i.e., R₂O=Li₂O+Na₂O). In one ormore embodiments, WO is the total amount of divalent metal oxidespresent in the alkali aluminosilicate glass. In one or more embodiments,the relationship R₂O (mol %)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol %) thatis greater than about −2.5 mol %, greater than about −2 mol %, greaterthan about −1.5 mol %, greater than about −1 mol %, greater than about−0.5 mol %, greater than about 0 mol %, greater than about 0.5 mol %,greater than about 1 mol %, greater than about 1.5 mol %, greater thanabout 2 mol %, greater than about 2.5 mol %, greater than about 3 mol %,greater than about 3.5 mol %, greater than about 4 mol %, greater thanabout 4.5 mol %, greater than about 5 mol %, greater than about 5.5 mol%, or greater than about 6 mol %, greater than about 6.5 mol %, greaterthan about 7 mol %, greater than about 7.5 mol %, greater than about 8mol %, greater than about 8.5 mol %, greater than about 9 mol %, orgreater than about 9.5 mol %.

Tables 1 lists exemplary compositions of the alkali aluminosilicateglasses described herein. Table 2 lists selected physical propertiesdetermined for the examples listed in Table 1. The physical propertieslisted in Table 2 include: density; low temperature and high temperatureCTE; strain, anneal and softening points; 10¹¹ Poise, 35 kP, 200 kP,liquidus, and zircon breakdown temperatures; zircon breakdown andliquidus viscosities; Poisson's ratio; Young's modulus; refractiveindex, and stress optical coefficient. In some embodiments, the glassesdescribed herein have a high temperature CTE of less than or equal to 30ppm/° C. and/or a Young's modulus of at least 70 GPa and, in someembodiments, a Young's modulus of up to 80 GPa.

TABLE 1 Examples of alkali aluminosilicate glass compositions.Composition Ex. Ex. Ex. Ex. Ex. Ex. Ex. (mol %) 1 2 3 4 5 6 7 SiO₂ 63.7764.03 63.67 63.91 64.16 63.21 63.50 Al₂O₃ 12.44 12.44 11.83 11.94 11.9411.57 11.73 P₂O₅ 2.43 2.29 2.36 2.38 1.92 1.93 1.93 Li₂O 0.00 0.00 0.000.00 0.00 0.00 0.00 Na₂O 16.80 16.81 16.88 16.78 16.80 17.63 16.85 ZnO0.00 4.37 0.00 4.93 0.00 5.59 5.93 MgO 4.52 0.02 5.21 0.02 5.13 0.020.01 SnO₂ 0.05 0.05 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.35 1.35 1.431.41 1.41 1.52 1.44 Li₂O/Na₂O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 (R₂O +RO) − 6.45 6.46 7.89 7.40 8.07 9.74 9.14 Al₂O₃ − P₂O₅ Composition Ex.Ex. Ex. Ex. Ex. Ex. Ex. (mol %) 8 9 10 11 12 13 14 SiO₂ 63.37 63.4363.56 63.58 63.66 63.62 63.67 Al₂O₃ 11.72 12.49 12.63 12.59 12.91 12.8512.89 P₂O₅ 2.00 2.32 2.46 2.46 2.43 2.45 2.47 Li₂O 0.00 0.00 1.42 2.870.00 1.42 2.92 Na₂O 16.84 17.16 15.45 14.04 16.89 15.48 13.92 ZnO 6.004.54 4.43 4.41 4.04 4.12 4.06 MgO 0.02 0.02 0.02 0.02 0.02 0.02 0.02SnO₂ 0.05 0.04 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.44 1.37 1.34 1.341.31 1.31 1.31 Li₂O/Na₂O 0.00 0.00 0.09 0.20 0.00 0.09 0.21 (R₂O + RO) −9.14 6.90 6.22 6.29 5.62 5.72 5.57 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex.Ex. Ex. Ex. Ex. (mol %) 15 16 17 18 19 20 21 SiO₂ 63.55 63.80 63.7663.88 63.74 64.03 63.68 Al₂O₃ 12.92 12.90 12.95 13.48 13.37 13.26 13.19P₂O₅ 2.35 2.34 2.37 2.31 2.34 2.29 2.46 Li₂O 0.00 1.47 2.94 0.00 1.482.94 0.00 Na₂O 17.97 16.36 14.85 17.20 15.96 14.37 16.84 ZnO 0.00 0.000.00 0.00 0.00 0.00 3.77 MgO 3.17 3.08 3.09 3.08 3.08 3.06 0.02 SnO₂0.05 0.04 0.05 0.05 0.04 0.04 0.05 R₂O/Al₂O₃ 1.39 1.38 1.37 1.28 1.301.31 1.28 Li₂O/Na₂O 0.00 0.09 0.20 0.00 0.09 0.20 0.00 (R₂O + RO) − 5.875.67 5.56 4.48 4.81 4.83 4.98 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex. Ex.Ex. Ex. Ex. (mol %) 22 23 24 25 26 27 28 SiO₂ 63.66 63.76 63.67 63.7363.73 63.64 63.76 Al₂O₃ 14.15 15.31 13.87 14.82 12.93 16.62 16.59 P₂O₅2.47 2.44 2.47 2.43 2.48 2.47 2.47 Li₂O 1.49 2.98 1.50 2.96 0.00 2.524.91 Na₂O 15.31 13.79 15.36 13.93 16.83 14.68 12.20 ZnO 2.85 1.64 0.000.00 2.98 0.00 0.00 MgO 0.03 0.03 3.09 2.08 1.00 0.03 0.03 SnO₂ 0.050.04 0.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 1.19 1.10 1.22 1.14 1.30 1.031.03 Li₂O/Na₂O 0.10 0.22 0.10 0.21 0.00 0.17 0.40 (R₂O + RO) − 3.05 0.703.61 1.72 5.40 −1.86 −1.92 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex. Ex. Ex.Ex. Ex. (mol %) 29 30 31 32 33 34 35 SiO₂ 63.89 63.92 63.77 63.73 63.7063.65 63.87 Al₂O₃ 16.55 15.29 15.27 15.30 15.27 15.22 15.29 P₂O₅ 2.472.24 2.31 2.39 2.40 2.48 2.37 Li₂O 7.27 3.46 2.98 4.02 4.46 4.96 5.39Na₂O 9.74 13.46 13.99 12.91 12.51 11.99 11.44 ZnO 0.00 1.56 1.61 1.571.58 1.63 1.57 MgO 0.03 0.02 0.02 0.03 0.03 0.02 0.02 SnO₂ 0.04 0.040.04 0.05 0.04 0.05 0.04 R₂O/Al₂O₃ 1.03 1.11 1.11 1.11 1.11 1.11 1.10Li₂O/Na₂O 0.75 0.26 0.21 0.31 0.36 0.41 0.47 (R₂O + RO) − −1.98 0.971.01 0.84 0.90 0.91 0.76 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex. Ex. Ex.Ex. Ex. (mol %) 36 37 38 39 40 41 42 SiO₂ 63.69 63.75 63.70 63.62 63.7463.77 63.77 Al₂O₃ 15.26 15.30 15.27 15.23 15.27 15.27 15.33 P₂O₅ 2.452.42 2.45 2.46 2.47 2.46 2.44 Li₂O 2.96 2.98 3.94 3.98 4.93 4.93 2.91Na₂O 13.50 13.46 12.54 12.57 11.49 11.50 13.94 ZnO 2.06 2.01 2.03 2.062.03 2.00 0.00 MgO 0.02 0.03 0.02 0.03 0.03 0.03 1.57 SnO₂ 0.05 0.040.04 0.05 0.04 0.05 0.04 R₂O/Al₂O₃ 1.08 1.08 1.08 1.09 1.08 1.08 1.10Li₂O/Na₂O 0.22 0.22 0.31 0.32 0.43 0.43 0.21 (R₂O + RO) − 0.83 0.77 0.800.95 0.73 0.73 0.66 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex. Ex. Ex. Ex. Ex.(mol %) 43 44 45 46 47 48 49 SiO₂ 63.69 63.81 63.65 63.71 63.62 63.6563.62 Al₂O₃ 15.25 15.26 15.33 15.32 15.24 15.68 15.67 P₂O₅ 2.43 2.412.46 2.44 2.47 2.44 2.48 Li₂O 4.00 4.89 2.96 4.01 4.91 6.07 6.06 Na₂O13.01 12.03 13.29 12.25 11.42 10.93 10.53 ZnO 0.00 0.00 2.24 2.20 2.271.17 1.57 MgO 1.57 1.56 0.03 0.03 0.02 0.02 0.02 SnO₂ 0.05 0.04 0.050.04 0.05 0.04 0.05 R₂O/Al₂O₃ 1.12 1.11 1.06 1.06 1.07 1.08 1.06Li₂O/Na₂O 0.31 0.41 0.22 0.33 0.43 0.56 0.58 (R₂O + RO) − 0.90 0.81 0.730.73 0.91 0.08 0.04 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex. Ex. Ex. Ex. Ex.(mol %) 50 51 52 53 54 55 56 SiO₂ 63.60 63.89 63.84 63.90 63.88 64.7460.17 Al₂O₃ 15.65 16.09 16.47 16.87 16.97 15.25 18.58 P₂O₅ 2.46 2.422.43 2.43 2.42 0.98 1.90 Li₂O 6.13 6.80 7.84 8.75 9.78 5.28 5.16 Na₂O10.29 9.97 8.96 7.99 6.88 12.09 12.58 ZnO 1.81 0.78 0.39 0.00 0.00 1.611.55 MgO 0.02 0.02 0.02 0.02 0.02 0.02 0.02 SnO₂ 0.04 0.04 0.04 0.040.04 0.03 0.03 R₂O/Al₂O₃ 1.05 1.04 1.02 0.99 0.98 1.14 0.96 Li₂O/Na₂O0.60 0.68 0.87 1.10 1.42 0.44 0.41 (R₂O + RO) − 0.14 −0.94 −1.68 −2.54−2.70 2.78 −1.16 Al₂O₃ − P₂O₅ Composition Ex. Ex. Ex. Ex. Ex. Ex. Ex.(mol %) 57 58 59 60 61 62 63 SiO₂ 58.32 63.3 63.3 63.3 63.3 63.3 63.3Al₂O₃ 18.95 15.25 15.65 16.2 15.1 15.425 15.7 P₂O₅ 2.42 2.5 2.5 2.5 2.52.5 2.5 Li₂O 4.96 6 7 7.5 6 7 7.5 Na₂O 13.74 10.7 9.7 9.45 10.55 9.4758.95 ZnO 1.56 1.2 0.8 0 2.5 2.25 2 MgO 0.02 1 1 1 0 0 0 SnO₂ 0.03 0.050.05 0.05 0.05 0.05 0.05 R₂O/Al₂O₃ 0.99 1.10 1.07 1.05 1.10 1.07 1.05Li₂O/Na₂O 0.36 0.56 0.72 0.79 0.57 0.74 0.84 (R₂O + RO) − −1.09 1.150.35 −0.75 1.45 0.80 0.25 Al₂O₃ − P₂O₅

TABLE 2 Selected physical properties of the glasses listed in Table 1.Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Density 2.434 2.493 2.4342.504 2.44 2.514 2.519 (g/cm³) Low 8.9 8.62 8.95 8.6 8.82 8.71 8.54temperature CTE 25-300° C. (ppm/° C.) High 17.67 19.1 17.16 21 18.12 2020.11 temperature CTE (ppm/° C.) Strain pt. (° C.) 630 591 612 580 605580 589 Anneal pt. (° C.) 683 641 662 628 651 629 639 10¹¹ Poise 770 725748 710 734 711 721 temperature (° C.) Softening pt. 937 888 919 873 909868 874 (° C.) T^(35 kP) (° C.) 1167 1180 1158 1160 T^(200 kP) (° C.)1070 1083 1061 1064 Zircon 1205 1220 1170 1185 1205 breakdowntemperature (° C.) Zircon 1.56 × 10⁴ 4.15 × 10⁴ 2.29 × 10⁴ 1.74 × 10⁴breakdown viscosity (P) Liquidus 980 990 975 990 1000 temperature (° C.)Liquidus 1.15 × 10⁶ 2.17 × 10⁶ 9.39 × 10⁵ 7.92 × 10⁵ viscosity (P)Poisson's ratio 0.200 0.211 0.206 0.214 0.204 0.209 0.211 Young's 69.268.8 69.4 68.5 69.6 68.3 69.0 modulus (GPa) Refractive 1.4976 1.50251.4981 1.5029 1.4992 1.5052 1.506 index at 589.3 nm Stress optical 2.9633.158 3.013 3.198 2.97 3.185 3.234 coefficient (nm/mm/MPa) Ex. 8 Ex. 9Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Density 2.516 2.501 2.498 2.493 2.4932.492 2.486 (g/cm³) Low 8.35 8.67 8.87 8.49 8.65 8.71 8.49 temperatureCTE 25-300° C. (ppm/° C.) High 20.11 20.6 20.94 19.52 20.77 temperatureCTE (ppm/° C.) Strain pt. (° C.) 590 589 591 584 600 579 588 Anneal pt.641 639 640 628 652 620 630 (° C.) 10¹¹ Poise 726 724 720 704 738 695704 temperature (° C.) Softening pt. 888 890 865 857 900 867 860 (° C.)T^(35 kP) (° C.) 1170 1176 1159 1139 1197 1169 T^(200 kP) (° C.) 10731080 1061 1041 1099 1070 Zircon 1195 1195 1210 1225 1195 1195 1220breakdown temperature (° C.) Zircon 2.33 × 10⁴ 2.58 × 10⁴ 1.60 × 10⁴9.94 × 10³ 3.63 × 10⁴ 2.35 × 10⁴ breakdown viscosity (P) Liquidus 1005990 990 980 990 980 980 temperature (° C.) Liquidus 8.69 × 10⁴ 1.48E+069.02E+05 7.10E+05 2.19E+06 1.33E+06 viscosity (P) Poisson's ratio 0.2110.205 0.208 0.209 0.209 0.210 0.217 Young's 69.0 68.7 71.4 73.5 68.471.6 74.0 modulus (GPa) Refractive 1.506 1.5036 1.505 1.5063 1.50261.5041 1.5052 index at 589.3 nm Stress optical 3.234 3.194 3.157 3.1313.18 3.156 3.131 coefficient (nm/mm/MPa) Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex.19 Ex. 20 Ex. 21 Density 2.433 2.429 2.426 2.431 2.428 2.433 2.486(g/cm³) Low 9.15 9.16 8.83 8.97 8.97 8.79 8.45 temperature CTE 25-300°C. (ppm/° C.) High 20 20 21 17.3 20 temperature CTE (ppm/° C.) Strainpt. (° C.) 615 606 599 633 616 611 602 Anneal pt. (° C.) 662 659 653 684670 665 653 10¹¹ Poise 747 745 741 771 758 751 739 temperature (° C.)Softening pt. 935 903 901 943 918 905 910 (° C.) T^(35 kP) (° C.) 11821166 1152 1221 1185 1167 1207 T^(200 kP) (° C.) 1083 1066 1051 1122 10841066 1108 Zircon breakdown temperature (° C.) Zircon breakdown viscosity(P) Liquidus temperature (° C.) Liquidus viscosity (P) Poisson's ratio0.203 0.207 0.205 0.209 0.199 0.207 Young's 68.9 71.2 72.7 69.4 70.968.1 modulus (GPa) Refractive 1.4964 1.4981 1.4991 1.4965 1.4984 1.50061.5019 index at 589.3 nm Stress optical 2.994 3.022 2.982 2.979 2.99 03.173 coefficient (nm/mm/MPa) Ex. 22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 Ex. 27Ex. 28 Density 2.468 2.448 2.434 2.428 2.47 2.419 2.414 (g/cm³) Low 8.68.23 8.91 8.25 8.66 8.52 8.17 temperature CTE 25-300° C. (ppm/° C.) High19.52 19.49 19.47 temperature CTE (ppm/° C.) Strain pt. (° C.) 596 595638 616 608 640 620 Anneal pt. 644 649 695 656 654 700 677 (° C.) 10¹¹Poise 728 741 785 732 736 798 771 temperature (° C.) Softening pt. 905922 941 925 911 978 946 (° C.) T^(35 kP) (° C.) 1217 1227 1209 1215 12091283 1249 T^(200 kP) (° C.) 1115 1125 1109 1115 1107 1184 1150 Zircon1185 1185 1180 1185 1185 breakdown temperature (° C.) Zircon 5.86E+046.91E+04 5.59E+04 5.72E+04 1.05E+05 breakdown viscosity (P) Liquidus 975980 1080 1025 940 temperature (° C.) Liquidus 4.14E+06 4.52E+06 3.56E+051.27E+06 2.92E+07 viscosity (P) Poisson's ratio 0.210 0.204 0.210 0.2120.213 Young's 71.4 71.6 73.5 68.8 76.9 modulus (GPa) Refractive 1.5021.5025 1.4996 1.5008 1.5006 1.4987 1.5014 index at 589.3 nm Stressoptical 3.123 3.03 3.001 3.021 3.148 3.039 3.015 coefficient (nm/mm/MPa)Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35 Density 2.408 2.4462.448 2.446 2.445 2.443 2.442 (g/cm³) Low 7.86 8.29 8.38 8.17 8.14 8.047.97 temperature CTE 25-300° C. (ppm/° C.) High 18.57 19.71 temperatureCTE (ppm/° C.) Strain pt. (° C.) 610 591 595 585 580 574 577 Anneal pt.665 645 649 638 633 627 629 (° C.) 10¹¹ Poise 755 736 740 726 722 717717 temperature (° C.) Softening pt. 924 915 919 894 894 895 890 (° C.)T^(35 kP) (° C.) 1216 1223 1227 1216 1210 1203 1196 T^(200 kP) (° C.)1120 1122 1126 1114 1108 1102 1095 Zircon 1210 1175 1180 1190 1195 12101205 breakdown temperature (° C.) Zircon 3.86E+04 7.72E+04 7.55E+045.29E+04 4.43E+04 3.14E+04 3.04E+04 breakdown viscosity (P) Liquidus1080 990 975 975 975 975 980 temperature (° C.) Liquidus 4.55E+053.28E+06 5.43E+06 3.80E+06 3.33E+06 3.02E+06 2.29E+06 viscosity (P)Poisson's ratio 0.211 0.206 0.202 0.21 0.204 0.204 0.203 Young's 75.073.91 73.02 74.60 74.67 75.15 75.43 modulus (GPa) Refractive 1.50531.503 1.5025 1.5035 1.5041 1.5046 1.5053 index at 589.3 nm Stressoptical 3.002 3.074 3.083 3.071 3.059 3.016 3.053 coefficient(nm/mm/MPa) Ex. 29 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35 Density2.408 2.446 2.448 2.446 2.445 2.443 2.442 (g/cm³) Low 7.86 8.29 8.388.17 8.14 8.04 7.97 temperature CTE 25-300° C. (ppm/° C.) High 18.5719.71 temperature CTE (ppm/° C.) Strain pt. (° C.) 610 591 595 585 580574 577 Anneal pt. 665 645 649 638 633 627 629 (° C.) 10¹¹ Poise 755 736740 726 722 717 717 temperature (° C.) Softening pt. 924 915 919 894 894895 890 (° C.) T^(35 kP) (° C.) 1216 1223 1227 1216 1210 1203 1196T^(200 kP) (° C.) 1120 1122 1126 1114 1108 1102 1095 Zircon 1210 11751180 1190 1195 1210 1205 breakdown temperature (° C.) Zircon 3.86E+047.72E+04 7.55E+04 5.29E+04 4.43E+04 3.14E+04 3.04E+04 breakdownviscosity (P) Liquidus 1080 990 975 975 975 975 980 temperature (° C.)Liquidus 4.55E+05 3.28E+06 5.43E+06 3.80E+06 3.33E+06 3.02E+06 2.29E+06viscosity (P) Poisson's ratio 0.211 0.206 0.202 0.21 0.204 0.204 0.203Young's 75.0 73.91 73.02 74.60 74.67 75.15 75.43 modulus (GPa)Refractive 1.5053 1.503 1.5025 1.5035 1.5041 1.5046 1.5053 index at589.3 nm Stress optical 3.002 3.074 3.083 3.071 3.059 3.016 3.053coefficient (nm/mm/MPa) Ex. 36 Ex. 37 Ex. 38 Ex. 39 Ex. 40 Ex. 41 Ex. 42Density 2.453 2.453 2.452 2.451 2.449 2.449 2.425 (g/cm³) Low 8.17 8.147.97 8.01 7.79 7.9 8.54 temperature CTE 25-300° C. (ppm/° C.) High 20.56temperature CTE (ppm/° C.) Strain pt. (° C.) 595 595 584 587 578 584 617Anneal pt. (° C.) 649 649 638 640 630 637 663 10¹¹ Poise 740 741 729 730718 726 746 temperature (° C.) Softening pt. 918 921 905 907 894 901 929(° C.) T^(35 kP) (° C.) 1229 1232 1212 1219 1200 1204 1232 T^(200 kP) (°C.) 1128 1131 1111 1118 1100 1103 1132 Zircon 1185 1200 1210 breakdowntemperature (° C.) Zircon 7.20E+04 4.26E+04 3.00E+04 breakdown viscosity(P) Liquidus 995 990 965 temperature (° C.) Liquidus 3.33E+06 2.51E+063.71E+06 viscosity (P) Poisson's ratio 0.208 0.206 0.206 Young's 73.7074.67 75.50 modulus (GPa) Refractive 1.5032 1.5042 1.5054 1.5005 indexat 589.3 nm Stress optical 3.093 3.071 3.072 3.033 coefficient(nm/mm/MPa) Ex. 43 Ex. 44 Ex. 45 Ex. 46 Ex. 47 Ex. 48 Ex. 49 Ex. 50Density 2.424 2.422 2.455 2.454 2.454 2.434 2.439 2.443 (g/cm³) Low 8.488.34 8.03 7.88 7.76 7.87 7.71 7.63 temperature coefficient of thermalexpansion 25 - 300° C. (ppm/° C.) High temperature coefficient ofthermal expansion (ppm/° C.) Strain pt. 614 594 595 586 579 580 581 579temperature (° C.) Anneal pt. 659 640 649 639 630 633 633 632temperature (° C.) 10¹¹ Poise 739 722 740 729 718 722 721 721temperature (° C.) Softening pt. 912 899 918 909 898 892 893 895temperature (° C.) 35 kP 1216 1204 1212 1200 1203 1203 1203 temperature(° C.) 200 kP 1116 1102 1113 1099 1105 1102 1103 temperature (° C.)Zircon breakdown temperature (° C.) Zircon breakdown viscosity (P)Liquidus 985 965 1005 1010 1030 temperature (° C.) Liquidus 4.E+061.78E+06 1.34E+06 8.98E+05 viscosity (P) Poisson's ratio 0.211 0.210.213 Young's 76.32 76.60 76.81 modulus (GPa) Refractive 1.5014 1.50261.5036 1.5047 1.5061 1.505 1.5059 1.5064 index at 589.3 nm Stressoptical 2.965 2.981 3.082 3.057 3.063 3.025 3.004 3.046 coefficient(nm/mm/MPa) Ex. 51 Ex. 52 Ex. 53 Ex. 54 Ex. 55 Ex. 56 Ex. 57 Density2.424 2.431 2.403 2.4 2.45 2.462 2.468 (g/cm³) Low 77.1 76.1 74.3 73.180.2 79.7 83.6 temperature CTE 25-300° C. (ppm/° C.) High temperatureCTE (ppm/° C.) Strain pt. (° C.) 588 599 611 612 580 611 597 Anneal pt.640 651 665 665 631 663 649 (° C.) 10¹¹ Poise 728 738 753 752 718 750735 temperature (° C.) Softening pt. 900.4 907.5 916 912.5 892.2 915.6899.4 (° C.) T^(35 kP) (° C.) 1204 1209 1209 1202 1206 1205 1184T^(200 kP) (° C.) 1106 1113 1113 1106 1102 1111 1093 Zircon breakdowntemperature (° C.) Zircon breakdown viscosity (P) Liquidus 1060 11151160 1205 temperature (° C.) Liquidus 5.11E+05 1.90E+05 8.18E+043.32E+04 viscosity (P) Poisson's ratio 0.211 0.212 0.208 0.214 Young's77.01 78.05 77.57 78.74 modulus (GPa) Refractive 1.5054 1.5055 1.50591.5072 index at 589.3 nm Stress optical 3.011 2.98 2.982 2.964coefficient (nm/mm/MPa)

Each of the oxide components of the base (or unstrengthened) andstrengthened (i.e., chemically strengthened by ion exchange) alkalialuminosilicate glass articles described herein serves a function and/orhas an effect on the manufacturability and physical properties of theglass. Silica (SiO₂), for example, is the primary glass forming oxide,and forms the network backbone for the molten glass. Pure SiO₂ has a lowCTE and is alkali metal-free. Due to its extremely high meltingtemperature, however, pure SiO₂ is incompatible with the fusion drawprocess. The viscosity curve is also much too high to match with anycore glass in a laminate structure. In one or more embodiments, thealkali aluminosilicate glass article comprises SiO₂ in an amount in arange from about 58 mol % to about 65 mol %, from about 59 mol % toabout 65 mol %, from about 60 mol % to about 65 mol %, from about 61 mol% to about 65 mol %, from about 62 mol % to about 65 mol %, from about63 mol % to about 65 mol %, from about 58 mol % to about 64 mol %, fromabout 58 mol % to about 63 mol %, from about 58 mol % to about 62 mol %,from about 58 mol % to about 61 mol %, from about 58 mol % to about 60mol %, from about 63 mol % to about 65 mol %, from about 63.2 mol % toabout 65 mol %, or from about 63.3 mol % to about 65 mol %.

In addition to silica, the alkali aluminosilicate glass articlesdescribed herein comprise the network formers Al₂O₃ to achieve stableglass formation, low CTE, low Young's modulus, low shear modulus, and tofacilitate melting and forming. Like SiO₂, Al₂O₃ contributes to therigidity to the glass network. Alumina can exist in the glass in eitherfourfold or fivefold coordination, which increases the packing densityof the glass network and thus increases the compressive stress resultingfrom chemical strengthening. In one or more embodiments, the alkalialuminosilicate glass article comprises Al₂O₃ in an amount in a rangefrom about 11 mol % to about 20 mol %, from about 12 mol % to about 20mol %, from about 13 mol % to about 20 mol %, from about 14 mol % toabout 20 mol %, from about 15 mol % to about 20 mol %, from about 11 mol% to about 19 mol %, from about 11 mol % to about 18.5 mol %, from about11 mol % to about 18 mol %, from about 11 mol % to about 17.5 mol %,from about 11 mol % to about 17 mol %, from about 11 mol % to about 16.5mol %, from about 11 mol % to about 16 mol %, from about 14 mol % toabout 17 mol %, from about 15 mol % to about 17 mol %, or from about 15mol % to about 16 mol %.

Phosphorous pentoxide (P₂O₅) is a network former incorporated in thealkali aluminosilicate glass articles described herein. P₂O₅ adopts aquasi-tetrahedral structure in the glass network; i.e., it iscoordinated with four oxygen atoms, but only three of which areconnected to the rest of the network. The fourth oxygen atom is aterminal oxygen that is doubly bound to the phosphorous cation. Theincorporation of P₂O₅ in the glass network is highly effective atreducing Young's modulus and shear modulus. Incorporating P₂O₅ in theglass network also reduces the high temperature CTE, increases theion-exchange interdiffusion rate, and improves glass compatibility withzircon refractory materials. In one or more embodiments, the alkalialuminosilicate glass article comprises P₂O₅ in an amount in a rangefrom about 0.5 mol % to about 5 mol %, from about 0.6 mol % to about 5mol %, from about 0.8 mol % to about 5 mol %, from about 1 mol % toabout 5 mol %, from about 1.2 mol % to about 5 mol %, from about 1.4 mol% to about 5 mol %, from about 1.5 mol % to about 5 mol %, from about1.6 mol % to about 5 mol %, from about 1.8 mol % to about 5 mol %, fromabout 2 mol % to about 5 mol %, from about 0.5 mol % to about 3 mol %,from about 0.6 mol % to about 3 mol %, from about 0.8 mol % to about 3mol %, from about 1 mol % to about 3 mol %, from about 1.2 mol % toabout 3 mol %, from about 1.4 mol % to about 3 mol %, from about 1.5 mol% to about 3 mol %, from about 1.6 mol % to about 3 mol %, from about1.8 mol % to about 3 mol %, from about 2 mol % to about 3 mol %, fromabout 0.5 mol % to about 2.8 mol %, from about 0.5 mol % to about 2.6mol %, from about 0.5 mol % to about 2.5 mol %, from about 0.5 mol % toabout 2.4 mol %, from about 0.5 mol % to about 2.2 mol %, from about 0.5mol % to about 2 mol %, from about 2.5 mol % to about 5 mol %, fromabout 2.5 mol % to about 4 mol %, or from about 2.5 mol % to about 3 mol%.

The alkali aluminosilicate glass articles described herein describedherein do not contain boron oxide (B₂O₃), or are free of B₂O₃ as itspresence has a negative impact on compressive stress when the glass isstrengthened by ion exchange. As used herein, the phrase “free of B₂O₃”means the alkali aluminosilicate glass articles described herein includeless than about 0.1 mol % B₂O₃, less than about 0.05 mol % B₂O₃ or lessthan about 0.01 mol %.

The alkali oxide Na₂O is used to achieve chemical strengthening of thealkali aluminosilicate glass articles described herein by ion exchange.The alkali aluminosilicate glass articles described herein include Na₂O,which provides the Na+ cation to be exchanged for potassium cationspresent in a salt bath containing, for example, KNO₃. In someembodiments, the alkali aluminosilicate glass articles described hereincomprise from about 4 mol % to about 20 mol % Na₂O. In one or moreembodiments, the alkali aluminosilicate glass article comprises Na₂O inan amount in a range from about 4.5 mol % to about 20 mol %, from about5 mol % to about 20 mol %, from about 5.5 mol % to about 20 mol %, fromabout 6 mol % to about 20 mol %, from about 6.5 mol % to about 20 mol %,from about 7 mol % to about 20 mol %, from about 7.5 mol % to about 20mol %, from about 8 mol % to about 20 mol %, from about 8.5 mol % toabout 20 mol %, from about 9 mol % to about 20 mol %, from about 9.5 mol% to about 20 mol %, from about 10 mol % to about 20 mol %, from about 4mol % to about 19.5 mol %, from about 4 mol % to about 19 mol %, fromabout 4 mol % to about 18.5 mol %, from about 4 mol % to about 18 mol %,from about 4 mol % to about 17.5 mol %, from about 4 mol % to about 17mol %, from about 4 mol % to about 16.5 mol %, from about 4 mol % toabout 16 mol %, from about 4 mol % to about 15.5 mol %, from about 4 mol% to about 15 mol %, from about 4 mol % to about 14.5 mol %, from about4 mol % to about 14 mol %, from about 6 mol % to about 18 mol %, fromabout 7 mol % to about 18 mol %, from about 8 mol % to about 18 mol %,from about 9 mol % to about 18 mol %, from about 6 mol % to about 12 mol%, from about 6 mol % to about 11 mol %, or from about 6 mol % to about10 mol %.

The alkali aluminosilicate glass articles described herein may, in someembodiments, further include up to about 13 mol % Li₂O or up to about 10mol % Li₂O. In some embodiments, the alkali aluminosilicate glassarticles comprise Li₂O in an amount in a range from about 0 mol % toabout 9.5 mol %, from about 0 mol % to about 9 mol %, from about 0 mol %to about 8.5 mol %, from about 0 mol % to about 8 mol %, from about 0mol % to about 7.5 mol %, from about 0 mol % to about 7 mol %, fromabout 0.1 mol % to about 10 mol %, from about 0.1 mol % to about 9.5 mol%, from about 0.1 mol % to about 9 mol %, from about 0.1 mol % to about8.5 mol %, from about 0.1 mol % to about 8 mol %, from about 0.1 mol %to about 7.5 mol %, from about 0.1 mol % to about 7 mol %, or from about4 mol % to about 8 mol %. When substituted for Na₂O, Li₂O reduces thezircon breakdown temperature and softens the glass, which allowsadditional Al₂O₃ to be added to the glass. In certain embodiments, thealkali aluminosilicate glass articles are free of Li₂O (i.e., contain 0mol % Li₂O), or substantially free of Li₂O. In the alkalialuminosilicate glass articles described herein, the amount of Na₂Opresent exceeds that of Li₂O, where Li₂O (mol %)/Na₂O (mol %)<1. In someembodiments, Li₂O (mol %)/Na₂O (mol %)<0.75. In some embodiments, R₂O(mol %)/Al₂O₃ (mol %)<2, and, in some embodiments, 0.9≤R₂O (mol %)/Al₂O₃(mol %)≤1.6, where R₂O=Li₂O+Na₂O.

The presence of potassium oxide in the glass has a negative effect onthe ability of to achieve high levels of surface compressive stress inthe glass through ion exchange. The alkali aluminosilicate glassarticles described herein, as originally formed, therefore do notcontain K₂O or are free of K₂O. In one or more embodiments, the alkalialuminosilicate glass articles include less than about 0.2 mol % K₂O.However, when ion exchanged in a potassium-containing molten salt (e.g.,containing KNO₃) bath, the alkali aluminosilicate glasses may includesome amount of K₂O (i.e., less than about 1 mol %), with the actualamount depending upon ion exchange conditions (e.g., potassium saltconcentration in the ion exchange bath, bath temperature, ion exchangetime, and the extent to which K⁺ ions replace Li⁺ and Na⁺ ions). Theresulting compressive layer will contain potassium—the ion-exchangedlayer near the surface of the glass may contain 10 mol % or more K₂O atthe glass surface, while the bulk of the glass at depths greater thanthe depth of the compressive layer remains essentially potassium-free.

In some embodiments, the alkali aluminosilicate glass articles describedherein may comprise from 0 mol % up to about 6 mol % ZnO (e.g., fromabout 0 mol % to about 5 mol %, from about 0 mol % to about 4 mol %,from about 0 mol % to about 3.5 mol %, from about 0 mol % to about 3 mol%, from about 0 mol % to about 2.5 mol %, from about 0.1 mol % to about6 mol %, from about 0.1 mol % to about 5 mol %, from about 0.1 mol % toabout 4 mol %, from about 0.1 mol % to about 3.5 mol %, from about 0.1mol % to about 3 mol %, from about 0.1 mol % to about 2.5 mol %, fromabout 0.1 mol % to about 2 mol %, from about 1 mol % to about 5 mol %,from about 2 mol % to about 5 mol %, from about 1 mol % to about 3 mol%, from about 1.5 mol % to about 3 mol %, from about 2 mol % to about 3mol %, or from about 1 mol % to about 2 mol %). The divalent oxide ZnOimproves the melting behavior of the glass by reducing the temperatureat 200 poise viscosity (200P temperature). ZnO also is beneficial inimproving the strain point when compared to like additions of P₂O₅,and/or Na₂O.

Alkaline earth oxides such as MgO and CaO, may also be substituted forZnO to achieve a similar effect on the 200P temperature and strainpoint. When compared to MgO and CaO, however, ZnO is less prone topromoting phase separation in the presence of P₂O₅. In some embodiments,the glasses described herein include from 0 mol % up to 6 mol % MgO or,in other embodiments, these glasses comprise from 0.02 mol % to about 6mol % MgO. While other alkaline earth oxides, including SrO and BaO, mayalso be substituted for ZnO, they are less effective in reducing themelt temperature at 200 poise viscosity than ZnO, MgO, or CaO and arealso less effective than ZnO, MgO, or CaO at increasing the strainpoint.

In some embodiments, the alkali aluminosilicate glass articles describedherein are formable by down-draw processes that are known in the art,such as slot-draw and fusion-draw processes. The glass compositions usedto form the alkali aluminosilicate glass articles may contain smallconcentrations of Li₂O and are compatible with the fusion-draw processand can be manufactured without issue. The lithium may be batched in themelt as either spodumene or lithium carbonate.

The fusion draw process is an industrial technique that has been usedfor the large-scale manufacture of thin glass sheets. Compared to otherflat glass manufacturing techniques, such as the float or slot drawprocesses, the fusion draw process yields thin glass sheets withsuperior flatness and surface quality. As a result, the fusion drawprocess has become the dominant manufacturing technique in thefabrication of thin glass substrates for liquid crystal displays, aswell as for cover glass for personal electronic devices such asnotebooks, entertainment devices, tables, laptops, and the like.

The fusion draw process involves the flow of molten glass over a troughknown as an “isopipe,” which is typically made of zircon or anotherrefractory material. The molten glass overflows the top of the isopipefrom both sides, meeting at the bottom of the isopipe to form a singlesheet where only the interior of the final sheet has made direct contactwith the isopipe. Since neither exposed surface of the final glass sheethas made contact with the isopipe material during the draw process, bothouter surfaces of the glass are of pristine quality and do not requiresubsequent finishing.

In order to be fusion drawable, a glass composition must have asufficiently high liquidus viscosity (i.e., the viscosity of a moltenglass at the liquidus temperature). In some embodiments, compositionsused to form the alkali aluminosilicate glass articles described hereinhave a liquidus viscosity of at least about 200 kilopoise (kP) and, inother embodiments, at least about 600 kP.

After the alkali aluminosilicate glass articles are formed, the articlemay be chemically strengthened. Ion exchange is widely used tochemically strengthen glasses. In one particular example, alkali cationswithin a source of such cations (e.g., a molten salt, or “ion exchange,”bath) are exchanged with smaller alkali cations within the glass toachieve a layer that is under a compressive stress near the surface ofthe glass article. The compressive layer extends from the surface to aDOL within the glass article. In the alkali aluminosilicate glassarticles described herein, for example, potassium ions from the cationsource are exchanged for sodium ions within the glass during ionexchange by immersing the glass in a molten salt bath comprising apotassium salt such as, but not limited to, potassium nitrate (KNO₃).Other potassium salts that may be used in the ion exchange processinclude, but are not limited to, potassium chloride (KCl), potassiumsulfate (K₂SO₄), combinations thereof, and the like. The ion exchangebaths described herein may contain alkali ions other than potassium andthe corresponding salts. For example, the ion exchange bath may alsoinclude sodium salts such as sodium nitrate (NaNO₃), sodium sulfate,sodium chloride, or the like. In one or more embodiments, a mixture oftwo different salts may be utilized. For example, the glass articles maybe immersed in a salt bath of KNO₃ and NaNO₃. In some embodiments, morethan one bath may be used with the glass being immersed in one bathfollowed by another, successively. The baths may have the same ordifferent compositions, temperatures and/or may be used for differentimmersion times.

The ion exchange bath may have a temperature in the range from about320° C. to about 450° C. Immersion time in the bath may vary from about15 minutes to about 16 hours.

While the embodiment shown in FIG. 1 depicts a strengthened alkalialuminosilicate glass article 100 as a flat planar sheet or plate, thealkali aluminosilicate glass article may have other configurations, suchas three dimensional shapes or non-planar configurations. Thestrengthened alkali aluminosilicate glass article 100 has a firstsurface 110 and a second surface 112 defining a thickness t. In one ormore embodiments, (such as the embodiment shown in FIG. 1) thestrengthened alkali aluminosilicate glass article is a sheet includingfirst surface 110 and opposing second surface 112 defining thickness t.The strengthened alkali aluminosilicate glass article 100 has a firstcompressive layer 120 extending from first surface 110 to a depth oflayer d₁ into the bulk of the glass article 100. In the embodiment shownin FIG. 1, the strengthened alkali aluminosilicate glass article 100also has a second compressive layer 122 extending from second surface112 to a second depth of layer dz. Glass article also has a centralregion 330 that extends from d₁ to d₂. Central region 130 is under atensile stress or central tension (CT), which balances or counteractsthe compressive stresses of layers 120 and 122. The depth d₁, d₂ offirst and second compressive layers 120, 122 protects the strengthenedalkali aluminosilicate glass article 100 from the propagation of flawsintroduced by sharp impact to first and second surfaces 110, 112 of thestrengthened alkali aluminosilicate glass article 100, while thecompressive stress minimizes the likelihood of a flaw penetratingthrough the depth d₁, d₂ of first and second compressive layers 120,122. DOL d1 and DOL d2 may be equal to one another or different from oneanother. In some embodiments, at least a portion of the central region(e.g., the portion extending from the DOL to a depth equal to 0.5 timesthe thickness of the article) may be free of K₂O (as defined herein).

The DOL may be described as a fraction of the thickness t (which isotherwise described herein as being in a range from about 0.05 mm toabout 1.5 mm). For example, in one or more embodiments, the DOL may beequal to or greater than about 0.1t, equal to or greater than about0.11t, equal to or greater than about 0.12t, equal to or greater thanabout 0.13t, equal to or greater than about 0.14t, equal to or greaterthan about 0.15t, equal to or greater than about 0.16t, equal to orgreater than about 0.17t, equal to or greater than about 0.18t, equal toor greater than about 0.19t, equal to or greater than about 0.2t, equalto or greater than about 0.21t. In some embodiments, The DOL may be in arange from about 0.08t to about 0.25t, from about 0.09t to about 0.25t,from about 0.18t to about 0.25t, from about 0.11t to about 0.25t, fromabout 0.12t to about 0.25t, from about 0.13t to about 0.25t, from about0.14t to about 0.25t, from about 0.15t to about 0.25t, from about 0.08tto about 0.24t, from about 0.08t to about 0.23t, from about 0.08t toabout 0.22t, from about 0.08t to about 0.21t, from about 0.08t to about0.2t, from about 0.08t to about 0.19t, from about 0.08t to about 0.18t,from about 0.08t to about 0.17t, from about 0.08t to about 0.16t, orfrom about 0.08t to about 0.15t. In some instances, the DOL may be about20 μm or less. In one or more embodiments, the DOL may be about 40 μm orgreater (e.g., from about 40 μm to about 300 μm, from about 50 μm toabout 300 μm, from about 60 μm to about 300 μm, from about 70 μm toabout 300 μm, from about 80 μm to about 300 μm, from about 90 μm toabout 300 μm, from about 100 μm to about 300 μm, from about 110 μm toabout 300 μm, from about 120 μm to about 300 μm, from about 140 μm toabout 300 μm, from about 150 μm to about 300 μm, from about 40 μm toabout 290 μm, from about 40 μm to about 280 μm, from about 40 μm toabout 260 μm, from about 40 μm to about 250 μm, from about 40 μm toabout 240 μm, from about 40 μm to about 230 μm, from about 40 μm toabout 220 μm, from about 40 μm to about 210 μm, from about 40 μm toabout 200 μm, from about 40 μm to about 180 μm, from about 40 μm toabout 160 μm, from about 40 μm to about 150 μm, from about 40 μm toabout 140 μm, from about 40 μm to about 130 μm, from about 40 μm toabout 120 μm, from about 40 μm to about 110 μm, or from about 40 μm toabout 100 μm.

In one or more embodiments, the strengthened alkali aluminosilicateglass article may have a maximum compressive stress (which may be foundat the surface or a depth within the glass article) of about 400 MPa orgreater, about 500 MPa or greater, about 600 MPa or greater, about 700MPa or greater, about 800 MPa or greater, about 900 MPa or greater,about 930 MPa or greater, about 1000 MPa or greater, or about 1050 MPaor greater.

In one or more embodiments, the strengthened alkali aluminosilicateglass article may have a maximum tensile stress or central tension (CT)of about 20 MPa or greater, about 30 MPa or greater, about 40 MPa orgreater, about 45 MPa or greater, about 50 MPa or greater, about 60 MPaor greater, about 70 MPa or greater, about 75 MPa or greater, about 80MPa or greater, or about 85 MPa or greater. In some embodiments, themaximum tensile stress or central tension (CT) may be in a range fromabout 40 MPa to about 100 MPa.

The alkali aluminosilicate glass articles described herein are, in someembodiments, ion-exchanged by immersion in a molten salt bath comprisingor consisting essentially of about 100% KNO₃ by weight (small amounts ofadditives such as silicic acid or the like may be added to the bath). Inorder to maximize the surface compressive stress, the glasses mayundergo a heat treatment followed by ion exchange. For articles having athickness of about 1 mm, the articles are ion exchanged for 45 minutesat 410° C. The glass articles are heat treated at the 10¹¹ Poise (P)temperature and rapidly quenched to set the fictive temperature toapproximately 10¹¹ P viscosity temperature prior to ion-exchange. Thisis done to set the fictive temperature to represent the thermal historyof a fusion drawn sheet. Table 3 lists the compressive stresses, depthsof compressive layer, and bend radii measured for the samples listed inTable 1 following ion exchange under the above conditions. Whensubjected to this combination of heat treatment followed by ionexchange, the alkali aluminosilicate glass articles described hereinhave a compressive layer having a maximum compressive stress CS of atleast about 1050 MPa and a depth of compressive layer DOL of less thanabout 25 μm or, in some embodiments, less than about 20 In someembodiments, the depth of the compressive layer is at least about 9

TABLE 3 Compressive stresses, depths of compressive layer, and bendradii measured for 1 mm thick samples, having compositions listed inTable 1, following setting the fictive temperature T_(F) to equal the10¹¹ P viscosity temperature and ion exchange at 410° C. for 45 minutesin a 100 wt % KNO₃ molten salt bath. Depth of Bend Compressive Layerradius¹ Example Stress (MPa) (μm) (mm) 1 1025 22 35.2 2 1026 22 35.1 3972 21 37.3 4 997 20 36.0 5 1047 18 34.7 6 1006 19 35.5 7 1024 18 35.3 81024 18 35.3 9 1020 21 35.2 10 1045 17 35.7 11 1030 15 37.3 12 1066 2233.5 13 1078 17 34.8 14 1040 15 37.4 15 1039 24 34.6 16 960 21 38.8 171035 20 36.7 18 1072 21 33.9 19 971 21 38.1 20 17 21 1069 22 33.3 221104 19 33.8 23 1105 17 24 1133 22 32.9 25 1145 18 33.6 26 1049 23 34.327 1097 21 28 1096 16 36.7 29 1099 13 35.7 30 1083 15 35.6 31 1080 1635.2 32 1136 14 34.3 33 1078 13 36.1 34 1097 12 35.7 35 1078 12 36.5 361079 15 35.7 37 38 1095 13 35.6 39 40 1087 12 36.3 41 42 1113 18 43 441127 14 45 1086 14 46 1113 13 47 1106 11 48 1105 11 36.2 49 1115 11 35.950 1097 10 36.7 51 1112 11 36.2 52 1121 11 36.4 53 1116 10 36.3 53 11279 36.6 ¹Bend radius (mm) required on ion exchanged glass samples toreduce net surface stress to 0 MPa.

In other embodiments, the alkali aluminosilicate glass articlesdescribed herein may be ion exchanged to achieve a deeper depth ofcompressive layer. For example, selected samples (the compositions ofwhich are listed in Table 1), each having a thickness of 1 mm, were ionexchanged for 8 hours at 410° C. in a molten salt bath comprising orconsisting essentially of about 100% KNO₃ to achieve depths of layer ofat least about 30 μm or, in some embodiments, at least about 40 μm, and,in still other embodiments, a depth of at least about 50 μm with amaximum compressive stress of at least about 930 MPa. Compressivestresses and depths of compressive layer measured for these samplesfollowing ion exchange under these conditions are listed in Table 4.

TABLE 4 Compressive stresses and depths of compressive layer measuredfor 1 mm thick samples, having compositions listed in Table 1, followingsetting the fictive temperature T_(F) to equal the 10¹¹ P viscositytemperature and ion exchange at 410° C. for 8 hours in a 100 wt % KNO₃molten salt bath. Compressive Depth of Example Stress (MPa) Layer (μm)30 955 54 33 941 48 35 938 42 36 979 52 38 977 47 45 990 50 46 978 45 51937 40 52 948 38 53 936 37 54 952 32

In still other embodiments, the alkali aluminosilicate glass articlesdescribed herein may be ion exchanged so as to obtain a deep depth ofcompressive layer and a stress profile that is parabolic or closelyapproximates a parabolic in the central tensile region of the glass. Forexample, selected samples (the compositions of which are listed in Table1), each having a thickness of 1 mm, were ion exchanged for 2, 4, or 16hours at 430° C. in a molten salt bath comprising or consistingessentially of about 100% NaNO₃ to achieve depths of compressive layerDOL of at least about 200 μm or, in some embodiments, up to about 25% ofthe total sample thickness t (i.e., DOL≤0.25t) and, in some embodiments,up to about 20% of the total sample thickness t (i.e., DOL≤0.2t) with amaximum tensile stress of at least about 30 MPa, or, in someembodiments, at least about 35 MPa or, in some embodiments, at leastabout 56 MPa, or, in still other embodiments, at least about 66 MPa.Central tensions and depths of compressive layer measured for thesesamples following ion exchange under these conditions are listed inTable 5.

TABLE 5 Central tensions and depths of compressive layer measured forselected samples (the compositions of which are listed in Table 1), eachhaving a thickness of 1 mm, following ion exchange for 2, 4, or 16 hoursat 430° C. in a molten salt bath comprising about 100 wt % NaNO₃. Ex. 34Ex. 40 Ex. 47 Ex. 48 Ex. 49 Ex. 50 Ion exchange for 2 hours at 430° C.in 100% NaNO₃ Central 62 71 68 69 Tension (MPa) Depth of 200 200 200 160Layer (μm) Ion exchange for 4 hours at 430° C. in 100% NaNO₃ Central 5859 56 63 70 66 Tension (MPa) Depth of 200 200 200 200 200 200 Layer (μm)Ion exchange for 16 hours at 430° C. in 100% NaNO₃ Central 40 38 41 3741 40 Tension (MPa) Depth of 200 200 200 200 200 200 Layer (μm)

The ion-exchange compressive stress can further be improved by annealingat the 10^(13.18) Poise temperature (the anneal point temperature) for30 minutes prior to ion-exchange. By relaxing the structure to a lowerfictive temperature state, the packing density of the glass isincreased, thus allowing for higher surface compressive stress throughion-exchange (at the expense of diffusivity).

The alkali aluminosilicate glass articles described herein exhibitsubstantially higher surface compressive stresses than other the alkalialuminosilicate glass articles in both the fusion state (Fictivetemperature (T_(f))=10¹¹ Poise temperature) and annealed state (Fictivetemperature=10¹³′ Poise temperature). Table 5 lists compressive stressCS, depth of the compressive layer, and the bend radius required tocancel out surface compressive stress on a 1 mm thick glass for twoexamples (examples 34 and 40) of the ion exchanged glasses describedherein and a comparative example having a nominal composition of 69 mol% SiO₂, 10 mol % Al₂O₃, 15 mol % Na₂O, 0.01 mol %, 5.5 mol % MgO, and0.2 mol % SnO₂. The comparative example is described in U.S. patentapplication Ser. No. 13/533,298, entitled “Ion Exchangeable Glass withHigh Compressive Stress”, filed Jun. 26, 2012, by Matthew John Dejnekaet al. All samples were heat treated at the anneal point temperature(temperature at the viscosity equals 10^(13.18) P) for 30 minutes priorto ion-exchange. The samples were ion exchanged at 410° C. for 45minutes in a molten KNO₃ salt bath.

As can be seen from Table 5, the comparative example was ion exchangedto achieve a compressive stress of 1118, whereas the glasses describedin the present disclosure were ion exchanged under the same conditionsto achieve compressive stresses of 1203 MPa and 1192 MPa. For glasseshaving higher surface compressive stress, the strength will be higherfor a given flaw size, and surface flaws remain under compression attighter bend radius, thus preventing fatigue (subcritical crack growth)of small flaws.

Since the small surface flaws under compression cannot extend tofailure, glasses with higher surface compressive stress are generallymore resistant to failure from bending events, although exceptions mayoccur for glasses with ultra-high modulus. The bend-induced stress hasto overcome the surface compressive stress to place the surface flawsinto tension. When bending a glass plate, the bend induced tensilestress at the surface is given by the following equation:

${\sigma = {\frac{E}{1 - \upsilon^{2}}\frac{h}{2}\frac{1}{R}}},$

where σ is the tensile stress on the outer surface of the glass, E isthe Young's modulus of the glass, υ is Poisson's ratio, h is thethickness of the glass, and R is the bend radius to the outer surface ofthe glass. The above equation may be rearranged to determine the bendradius required to reduce the ion-exchange surface stress to zero:

$R = {\frac{E}{1 - \upsilon^{2}}\frac{h}{2}\frac{1}{\sigma_{IOX}}}$

Glasses that require a smaller bend radius to overcome the ion-exchangesurface stress are more resistant to bend induced failure by propagationof surface flaws. Calculating the R value for the glass of the abovecomparative example (E=71.3, Poisson's ratio=0.205, IOX surfacestress=1014 MPa), we determine that a bend radius of 36.7 mm will reducethe surface stress to 0 MPa. In contrast, the examples listed in Table 1of glasses described hereinabove with T_(F)=10¹¹ P temperature willrequire a bend radius of less than 36 mm to reduce the net surfacestress to 0 MPa.

TABLE 5 Results of ion exchange of glass samples. Comparative exampleEx. 34 Ex. 40 CS (MPa) 1118 1203 1192 DOL (μm) 12 11 10 Bend radius (mm)33.3 32.6 33.1

Table 6 lists exemplary compositions of the alkali aluminosilicate glassarticles described herein. Table 7 lists selected physical propertiesdetermined for the examples listed in Table 6. The physical propertieslisted in Table 7 include: density; CTE; strain, anneal and softeningpoints; liquidus temperature; liquidus viscosity; Young's modulus;refractive index, and stress optical coefficient.

TABLE 6 Examples of alkali aluminosilicate glass articles. CompositionEx. Ex. Ex. Ex. Ex. Ex. Ex. (mol %) 58 59 60 61 62 63 64 Al₂O₃ 16.6716.73 16.70 16.73 16.17 16.13 15.73 B₂O₃ Cs₂O 0.46 Li₂O 7.46 7.41 7.307.42 7.45 7.54 7.45 Na₂O 8.75 8.28 7.77 7.85 8.30 7.76 8.77 P₂O₅ 3.463.95 3.94 3.92 3.45 3.94 3.38 SiO₂ 63.62 63.58 64.24 63.56 63.61 63.6163.71 SnO₂ 0.05 0.05 0.05 0.05 0.05 0.05 ZnO 0.98 0.97 0.96 R₂O 16.2115.69 15.07 15.27 15.75 15.30 16.22 B₂O₃ + 83.74 84.26 84.88 84.22 83.2383.68 82.82 P₂O₅ + SiO₂ + Al₂O₃ Composition (mol %) Ex. 65 Ex. 66 Ex. 67Al₂O₃ 15.65 16.68 16.66 B₂O₃ Cs₂O Li₂O 7.47 9.99 12.38 Na₂O 8.27 7.324.84 P₂O₅ 3.91 2.45 2.44 SiO₂ 63.67 63.50 63.63 SnO₂ 0.05 0.05 0.05 ZnO0.98 R2O 15.74 17.31 17.22 B₂O₃ + P₂O₅ + 83.23 82.64 82.73 SiO₂ + Al₂O₃

TABLE 7 Selected physical properties of the glasses listed in Table 6.Ex. 58 Ex. 59 Ex. 60 Ex. 61 Ex. 62 Ex. 63 Ex. 64 Fulchers A −3.933−3.681 −3.994 −4.132 −4.049 −3.657 −4.147 Fulchers B 10000.7 9453.710199.7 10556.7 10414.5 9531.9 10785.5 Fulchers To 50.4 85.5 41.3 22.6−0.8 50.1 −38.5 200 P 1655 1666 1662 1664 1639 1650 1634 Temperature (°C.) 35000 P 1230 1235 1236 1239 1211 1212 1202 Temperature (° C.) 200000P 1133 1138 1139 1142 1113 1114 1103 Temperature (° C.) Density 2.3962.389 2.389 2.413 2.413 2.406 2.415 (g/cm³) CTE 73.9 71.7 72.5 72.8 71.569 74.7 25-300° C. (ppm/° C.) Strain pt. (° C.) 606 605 604 605 587 589578 Anneal pt. (° C.) 661 662 661 661 642 644 631 Softening pt. 926.4931.7 930.3 935.1 908.6 912.3 898.4 (° C.) Liquidus 1080 1095 1090 10951080 1100 1055 temperature (° C.) Liquidus 602823 482764 539563 515222386294 264159 520335 viscosity (P) Stress optical 30.04 30.43 30.43 30.430.51 3.083 30.34 coefficient (nm/mm/MPa) Refractive 1.5016 1.50031.5003 1.5010 1.5037 1.5021 1.5035 index at 589.3 nm Young's 75.84 75.5775.70 75.15 76.67 75.77 76.12 modulus (GPa) Ex. 58 Ex. 59 Ex. 60Fulchers A −3.649 −3.231 −2.918 Fulchers B 9623.9 8275.1 7331.7 FulchersTo 33.9 126.8 188.3 200 P Temperature (° C.) 1651 1623 1593 35000 PTemperature (° C.) 1209 1191 1171 200000 P Temperature (° C.) 1109 10971080 Density (g/cm³) 2.408 2.401 2.394 CTE 71.7 74.5 70.4 25-300° C.(ppm/° C.) Strain pt. (° C.) 579 607 607 Anneal pt. (° C.) 633 656 656Softening pt. (° C.) 898.7 900.7 900 Liquidus temperature (° C.) 10901180 1265 Liquidus viscosity (P) 290856 42277 7788 Stress opticalcoefficient 3.028 2.937 2.926 (nm/mm/MPa) Refractive index at 589.3 nm1.5022 1.5071 1.5099 Young's modulus (GPa) 75.84 78.60 79.91

Examples 58-65 were formed into glass articles (having a sheet form andspecific thickness) and then chemically strengthened by immersing in amolten salt bath having a specific temperature, for a specifiedduration. Table 8 shows the thickness of each glass article, thechemical strengthening conditions, and the measured maximum CT and DOCvalues of the resulting strengthened glass article.

TABLE 8 Chemical strengthening conditions and resulting attributes ofselected strengthened alkali aluminosilicate glass articles. Ex. 58 Ex.59 Ex. 60 Ex. 61 Immersion in a molten salt bath of 100% NaNO₃ having atemperature of 390° C. for 4 hours Thickness (mm) 1.07 1.11 1.11 1.05Maximum CT (MPa) 81 76 72 74 DOC as a fraction of 0.19 0.19 0.19 0.17thickness Immersion in a molten salt bath of 100% NaNO₃ having atemperature of 390° C. for 6 hours Thickness (mm) 1.08 1.1 1.12 1.04Maximum CT (MPa) 89 80 87 86 DOC as a fraction of 0.18 0.2 0.19 0.19thickness Immersion in a molten salt bath of 100% NaNO₃ having atemperature of 390° C. for 8 hours Thickness (mm) 1.07 1.1 1.11 1.03Maximum CT (MPa) 88 83 84 87 DOC as a fraction of 0.19 0.2 0.2 0.17thickness Ex. 62 Ex. 63 Ex. 64 Ex. 65 Immersion in a molten salt bath of100% NaNO₃ having a temperature of 390° C. for 4 hours Thickness (mm)1.05 1.02 1.09 1.09 Maximum CT (MPa) 81 82 77 73 DOC as a fraction of0.17 0.16 0.17 0.18 thickness Immersion in a molten salt bath of 100%NaNO₃ having a temperature of 390° C. for 6 hours Thickness (mm) 1.081.03 1.07 1.1 Maximum CT (MPa) 81 82 85 85 DOC as a fraction of 0.2 0.20.19 0.2 thickness Immersion in a molten salt bath of 100% NaNO₃ havinga temperature of 390° C. for 8 hours Thickness (mm) 1.06 1.04 1.09 1.1Maximum CT (MPa) 84 87 84 83 DOC as a fraction of 0.18 0.18 0.2 0.19thickness

In another aspect, a laminate comprising the alkali aluminosilicateglasses described herein is also provided. A schematic cross-sectionalview of the laminate is shown in FIG. 2. The laminate 200 comprises analkali aluminosilicate glass article 200 (which may be provided as asheet) and a second article 220 (which may also be provided as a sheet).As shown in FIG. 2, the sheet of alkali aluminosilicate glass articlemay be joined to the transparent substrate 220.

In one or more embodiments, the second article 220 has a refractiveindex that is within 5% of the refractive index of the alkalialuminosilicate glass sheet 210. By closely matching the refractiveindices of the second article 220 and the alkali aluminosilicate glasssheet 210, the laminate 200 is transparent and exhibits little haze(e.g., less than about 20% or, in some embodiments, less than 10% at aviewing angle of 90° to the surface). The second article 220 maycomprise a second sheet of the alkali aluminosilicate glass used insheet 210, and may have a thickness and/or composition that differs fromthose of sheet 210. In some embodiments, the second article 220 includesa sheet of soda lime glass, or borosilicate glass. Alternatively, aplastic material such as polycarbonate or the like may serve as thesecond article 220 so long as the previously mentioned criteria foroptical quality are met.

In one embodiment, the alkali aluminosilicate glass sheet 210 is joinedto the second article 220 by a bonding layer 215. The bonding layer 215is also transparent and may comprise those bonding agents or materials,such as adhesives, epoxies, resins, frit materials or the like that areknown in the art to be suitable for such purposes and have the desiredoptical properties. In one embodiment, the bonding layer 215 has arefractive index that is within 5% of the refractive index of the alkalialuminosilicate glass sheet 210 and the second article 220, in order toprovide high optical quality with little haze and/or distortion.Alternatively, the alkali aluminosilicate glass sheet 210 and secondarticle 220 may be bonded directly to each other by way of fusion. Inone such embodiment, the alkali aluminosilicate glass sheet 210 andsecond article 220 may be simultaneously fusion drawn such that thesurfaces of the two fusion drawn sheets contact each other and thus bondtogether to form the laminate.

In some embodiments, the alkali aluminosilicate glass articles andlaminates described herein form a portion of a consumer electronicproduct, such as a cellular phone or smart phone, laptop computers,tablets, or the like. A schematic view of a consumer electronic product(e.g., a smart phone) is shown in FIGS. 3 and 4. Consumer electronicproduct 1000 typically comprises a housing 1020 having a front surface1040, a back surface 1060, and side surfaces 1080; and includeselectrical components (not shown), which are at least partially internalto the housing 1020. The electrical components include at least a powersource, a controller, a memory, and a display 1120. The display 1120 is,in some embodiments, provided at or adjacent the front surface 312 ofthe housing. A cover glass 100, 100 a, which comprises an embodiment ofthe strengthened alkali aluminosilicate glass articles described herein,is provided at or over the front surface 1040 of the housing 1020 suchthat the cover glass 100, 100 a is positioned over the display 1120 andprotects the display 1120 from damage caused by impact or damage. Thecover glass 100 has a thickness of from about 0.4 mm to about 2.5 mmand, when chemically strengthened, a maximum compressive stress of atleast 400 MPa at the surface of the cover glass 100. In someembodiments, the cover glass has a thickness of at least 1 mm and has amaximum compressive stress at the surface of at least 1050 MPa and adepth of layer of up to about 25 μm. In other embodiments, the coverglass has a thickness of at least 1 mm and has a maximum compressivestress at the surface of at least about 930 MPa and a depth of layer ofat least about 40 μm.

Aspect (1) of this disclosure pertains to an alkali aluminosilicateglass article comprising: a compressive stress layer extending from asurface of the alkali aluminosilicate glass to a depth of layer (DOL),the compressive stress layer having a maximum compressive stress of atleast 400 MPa at the surface, wherein the alkali aluminosilicate glassarticle comprises at least about 58 mol % SiO₂, from about 0.5 mol % toabout 3 mol % P₂O₅, at least about 11 mol % Al₂O₃, Na₂O and Li₂O,wherein the ratio of the amount of Li₂O (mol %) to Na₂O (mol %)(Li₂O/Na₂O) is less than 1.0, and wherein the alkali aluminosilicateglass article is free of B₂O₃.

Aspect (2) of this disclosure pertains to the alkali aluminosilicateglass article according to Aspect (1), wherein the alkalialuminosilicate glass article comprises a fictive temperature T_(f) thatis equal to a temperature at which the alkali aluminosilicate glassarticle has a viscosity of 10¹¹ Poise.

Aspect (3) of this disclosure pertains to the alkali aluminosilicateglass article according to Aspect (1) or Aspect (2), wherein the alkalialuminosilicate glass article comprises a zircon breakdown temperatureof less than about 35 kPoise.

Aspect (4) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (3), whereinthe alkali aluminosilicate glass article comprises a liquidus viscosityof at least 200 kPoise.

Aspect (5) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (4), whereinthe alkali aluminosilicate glass article comprises a ratio R₂O (mol%)/Al₂O₃ (mol %) that is less than 2, where R₂O=Li₂O+Na₂O.

Aspect (6) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (5), whereinthe alkali aluminosilicate glass article comprises a total amount ofSiO₂ and P₂O₅ that is greater than 65 mol % and less than 67 mol % (65mol %<SiO₂ (mol %)+P₂O₅ (mol %)<67 mol %).

Aspect (7) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (6), whereinthe alkali aluminosilicate glass article comprises a relationship R₂O(mol %)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol %) that is greater thanabout −3 mol %, wherein R₂O=the total amount of Li₂O and Na₂O present inthe alkali aluminosilicate glass article and WO is a total amount ofdivalent metal oxides present in the alkali aluminosilicate glassarticle.

Aspect (8) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (7), whereinthe alkali aluminosilicate glass article comprises from about 58 mol %to about 65 mol % SiO₂; from about 11 mol % to about 20 mol % Al₂O₃;from about 6 mol % to about 18 mol % Na₂O; from 0 mol % to about 6 mol %MgO; and from 0 mol % to about 6 mol % ZnO.

Aspect (9) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (8), whereinthe alkali aluminosilicate glass article comprises P₂O₅ in an amount ina range from about 0.5 mol % to about 2.8 mol %.

Aspect (10) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (9), whereinthe alkali aluminosilicate glass article comprises Li₂O in an amount upto about 10 mol % Li₂O.

Aspect (11) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (10), whereinthe article comprises a thickness in a range from about 0.05 mm to about1.5 mm.

Aspect (12) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (11), whereinthe glass article comprises a thickness of at least 1 mm, and whereinthe maximum compressive stress is at least about 1050 MPa at thesurface.

Aspect (13) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (12), whereinthe glass article comprises a thickness of at least 1 mm, and whereinthe maximum compressive stress is at least about 930 MPa at the surface.

Aspect (14) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (13), whereinthe glass is chemically strengthened.

Aspect (15) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (14), whereinthe article comprises a thickness and a central region extending fromthe DOL to a depth equal to 0.5 times the thickness, and wherein thecentral region is free of K₂O.

Aspect (16) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (15), whereinthe glass has a bend radius of less than about 37 mm at a thickness ofabout 1 mm.

Aspect (17) of this disclosure pertains to the alkali aluminosilicateglass article according Aspect (16), wherein the bend radius is lessthan about 35 mm.

Aspect (18) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (1) through (17), whereinthe alkali aluminosilicate glass has a tensile region extending from thedepth of layer into the glass article, wherein the tensile region has amaximum tensile stress of less than about 20 MPa or greater than about40 MPa.

Aspect (19) of this disclosure pertains to a laminate comprising thealkali aluminosilicate glass article according to any one of Aspects (1)through (18), and a second article.

Aspect (20) of this disclosure pertains to a consumer electronic devicecomprising: a housing; electrical components provided at least partiallyinternal to the housing, the electrical components including at least acontroller, a memory, and a display, the display being provided at oradjacent to a front surface of the housing; and a cover article disposedat or over the front surface of the housing and over the display,wherein the cover article comprises the alkali aluminosilicate glassarticle according to any one of Aspects (1) through (19).

Aspect (21) of this disclosure pertains to an alkali aluminosilicateglass article comprising: a thickness t, a compressive stress layerextending from a surface of the alkali aluminosilicate glass to a depthof layer (DOL), and a central region comprising a maximum tensilestress, wherein the central region extends from the DOL, and wherein thealkali aluminosilicate glass is free of B₂O₃ and comprises at leastabout 58 mol % SiO₂, from about 0.5 mol % to about 3 mol % P₂O₅, atleast about 11 mol % Al₂O₃, Na₂O and, Li₂O, wherein the ratio of theamount of Li₂O (mol %) to Na₂O (mol %) (Li₂O/Na₂O) is less than 1.0,wherein the DOL is less than or equal to 0.25*t, and wherein the maximumtensile stress is about 35 MPa or greater.

Aspect (22) of this disclosure pertains to the alkali aluminosilicateglass article according to Aspect (21), wherein the glass articlefurther comprises a tensile stress profile in the central region,wherein the tensile stress profile is substantially parabolic.

Aspect (23) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (22), whereinthe alkali aluminosilicate glass article comprises a fictive temperatureT_(f) that is equal to a temperature at which the alkali aluminosilicateglass article has a viscosity of 10¹¹ Poise.

Aspect (24) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (23), whereinthe alkali aluminosilicate glass article comprises a zircon breakdowntemperature of less than about 35 kPoise.

Aspect (25) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (24), whereinthe alkali aluminosilicate glass article comprises a liquidus viscosityof at least 200 kPoise.

Aspect (26) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (25), whereinthe alkali aluminosilicate glass article comprises a ratio R₂O (mol%)/Al₂O₃ (mol %) that is less than 2, where R₂O=Li₂O+Na₂O.

Aspect (27) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (26), whereinthe alkali aluminosilicate glass article comprises a total amount ofSiO₂ and P₂O₅ that is greater than 65 mol % and less than 67 mol % (65mol %<SiO₂ (mol %)+P₂O₅ (mol %)<67 mol %).

Aspect (28) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (27), whereinthe alkali aluminosilicate glass article comprises a relationship R₂O(mol %)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol %) that is greater thanabout −3 mol %, wherein R₂O=the total amount of Li₂O and Na₂O present inthe alkali aluminosilicate glass article and WO is a total amount ofdivalent metal oxides present in the alkali aluminosilicate glassarticle.

Aspect (29) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (28), whereinthe alkali aluminosilicate glass article comprises from about 58 mol %to about 65 mol % SiO₂; from about 11 mol % to about 20 mol % Al₂O₃;from about 6 mol % to about 18 mol % Na₂O; from 0 mol % to about 6 mol %MgO; and from 0 mol % to about 6 mol % ZnO.

Aspect (30) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (29), whereinthe alkali aluminosilicate glass article comprises P₂O₅ in an amount ina range from about 0.5 mol % to about 2.8 mol %.

Aspect (31) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (30), whereinthe alkali aluminosilicate glass article comprises Li₂O in an amount upto about 10 mol % Li₂O.

Aspect (32) of this disclosure pertains to the alkali aluminosilicateglass article according to any one of Aspects (21) through (31), whereinthe alkali aluminosilicate glass article is free of K₂O.

Aspect (33) pertains to a device comprising: a housing having front,back, and side surfaces; electrical components that are at leastpartially inside the housing; a display at or adjacent to the frontsurface of the housing; and a strengthened alkali aluminosilicate glassarticle disposed over the display, wherein the strengthened alkalialuminosilicate glass article comprises a compressive stress layerextending from a surface of the alkali aluminosilicate glass article toa depth of layer (DOL), the compressive layer having a maximumcompressive stress of at least 400 MPa at the surface, wherein thealkali aluminosilicate article comprises at least about 58 mol % SiO₂,from about 0.5 mol % to about 3 mol % P₂O₅, at least about 11 mol %Al₂O₃, Na₂O and Li₂O, wherein the ratio of the amount of Li₂O (mol %) toNa₂O (mol %) (Li₂O/Na₂O) is less than 1.0, and wherein the alkalialuminosilicate glass article is free of B₂O₃.

Aspect (34) pertains to the device of Aspect (33), wherein the alkalialuminosilicate glass article comprises a fictive temperature T_(f) thatis equal to a temperature at which the alkali aluminosilicate glassarticle has a viscosity of 10¹¹ Poise.

Aspect (35) pertains to the device of any one of Aspects (33) through(34), wherein the alkali aluminosilicate glass article comprises azircon breakdown temperature of less than about 35 kPoise.

Aspect (36) pertains to the device of any one of Aspects (33) through(35), wherein alkali aluminosilicate glass article comprises a liquidusviscosity of at least 200 kPoise.

Aspect (37) pertains to the device of any one of Aspects (33) through(36), wherein the alkali aluminosilicate glass article comprises a ratioR₂O (mol %)/Al₂O₃ (mol %) that is less than 2, where R₂O=Li₂O+Na₂O.

Aspect (38) pertains to the device of any one of Aspects (33) through(37), wherein the alkali aluminosilicate glass article comprises a totalamount of SiO₂ and P₂O₅ that is greater than 65 mol % and less than 67mol % (65 mol %<SiO₂ (mol %)+P₂O₅ (mol %)<67 mol %).

Aspect (39) pertains to the device of any one of Aspects (33) through(38), wherein the alkali aluminosilicate glass article comprises arelationship R₂O (mol %)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol %) that isgreater than about −3 mol %, wherein R₂O=the total amount of Li₂O andNa₂O present in the alkali aluminosilicate glass article and WO is atotal amount of divalent metal oxides present in the alkalialuminosilicate glass article.

Aspect (40) pertains to the device of any one of Aspects (33) through(39), wherein the alkali aluminosilicate glass article comprises fromabout 58 mol % to about 65 mol % SiO₂; from about 11 mol % to about 20mol % Al₂O₃; from about 6 mol % to about 18 mol % Na₂O; from 0 mol % toabout 6 mol % MgO; and from 0 mol % to about 6 mol % ZnO.

Aspect (41) pertains to the device of any one of Aspects (33) through(40), wherein the alkali aluminosilicate glass article comprises P₂O₅ inan amount in a range from about 0.5 mol % to about 2.8 mol %.

Aspect (42) pertains to the device of any one of Aspects (33) through(41), wherein the alkali aluminosilicate glass article comprises Li₂O inan amount up to about 10 mol % Li₂O.

Aspect (43) pertains to the device of any one of Aspects (33) through(42), wherein the alkali aluminosilicate glass has a thickness in arange from about 0.05 mm to about 1.5 mm.

Aspect (44) pertains to the device of any one of Aspects (33) through(43), wherein the glass article further comprises a thickness of atleast 1 mm, wherein the maximum compressive stress is at least about1050 MPa at the surface.

Aspect (45) pertains to the device of any one of Aspects (33) through(44), wherein the glass article further comprises a thickness of atleast 1 mm, wherein the maximum compressive stress is at least about 930MPa at the surface.

Aspect (46) pertains to the device of any one of Aspects (33) through(45), wherein the depth of layer is at least 40 μm.

Aspect (47) pertains to the device of any one of Aspects (33) through(46), wherein the alkali aluminosilicate glass is chemicallystrengthened.

Aspect (48) pertains to the device of any one of Aspects (33) through(47), wherein the glass article further comprises a thickness and acentral region extending from the DOL to a depth equal to 0.5 times thethickness, and wherein the central region is free of K₂O.

Aspect (49) pertains to the device of any one of Aspects (33) through(48), wherein the device comprises a mobile electronic communication andentertainment device selected from the group consisting of a mobilephone, a smart phone, a tablet, a video player, an information terminal(IT) device, a music player, and a laptop computer.

Aspect (50) pertains an alkali aluminosilicate glass article comprising:at least about 58 mol % SiO₂, from about 0.5 mol % to about 3 mol %P₂O₅, at least about 11 mol % Al₂O₃, Na₂O and Li₂O, wherein the alkalialuminosilicate glass article is free of B₂O₃ and K₂O, and wherein theratio of the amount of Li₂O (mol %) to Na₂O (mol %) (Li₂O/Na₂O) is lessthan 1.0.

Aspect (51) pertains to the alkali aluminosilicate glass article ofAspect (50) wherein the alkali aluminosilicate glass article comprisesP₂O₅ in an amount in a range from about 0.5 mol % to about 2.8 mol %.

Aspect (52) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (51), wherein the alkali aluminosilicateglass article comprises Li₂O in an amount up to about 10 mol % Li₂O.

Aspect (53) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (52), wherein the alkali aluminosilicateglass article comprises a fictive temperature T_(f) that is equal to atemperature at which the alkali aluminosilicate glass has a viscosity of10¹¹ Poise.

Aspect (54) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (53), wherein the alkali aluminosilicateglass article comprises a zircon breakdown temperature of less thanabout 35 kPoise.

Aspect (55) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (54), wherein the alkali aluminosilicateglass article comprises a liquidus viscosity of at least 200 kPoise.

Aspect (56) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (55), wherein the alkali aluminosilicateglass article comprises a ratio R₂O (mol %)/Al₂O₃ (mol %) that is lessthan 2, where R₂O=Li₂O+Na₂O.

Aspect (57) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (56), wherein the alkali aluminosilicateglass article comprises a total amount of SiO₂ and P₂O₅ that is greaterthan 65 mol % and less than 67 mol % (65 mol %<SiO₂ (mol %)+P₂O₅ (mol%)<67 mol %).

Aspect (58) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (57), wherein the alkali aluminosilicateglass article comprises a relationship R₂O (mol %)+R′O (mol %)−Al₂O₃(mol %)+P₂O₅ (mol %) that is greater than about −3 mol %, whereinR₂O=the total amount of Li₂O and Na₂O present in the alkalialuminosilicate glass article and WO is a total amount of divalent metaloxides present in the alkali aluminosilicate glass article.

Aspect (59) pertains to the alkali aluminosilicate glass article of anyone of Aspects (50) through (58), wherein the alkali aluminosilicateglass article comprises from about 58 mol % to about 65 mol % SiO₂; fromabout 11 mol % to about 20 mol % Al₂O₃; from about 6 mol % to about 18mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0 mol % to about6 mol % ZnO.

Aspect (60) pertains to a laminate comprising the alkali aluminosilicateglass article of any one of Aspects (50) through (59), and a secondarticle.

Aspect (61) pertains to a device comprising: a housing having front,back, and side surfaces; electrical components that are at leastpartially inside the housing; a display at or adjacent to the frontsurface of the housing; and the alkali aluminosilicate glass article ofany one of Aspects (50) through (60).

Aspect (62) pertains to a method of making a strengthened alkalialuminosilicate glass, the alkali aluminosilicate glass having acompressive stress layer, the method comprising: generating acompressive stress in an alkali aluminosilicate glass article by ionexchanging the aluminosilicate glass article, wherein the alkalialuminosilicate is free of B₂O₃ and K₂O and comprises at least about 58mol % SiO₂, from about 0.5 mol % to about 3 mol % P₂O₅, at least about11 mol % Al₂O₃, Na₂O and, Li₂O, wherein the ratio of the amount of Li₂O(mol %) to Na₂O (mol %) (Li₂O/Na₂O) is less than 1.0, wherein thecompressive stress layer extends from a surface of the alkalialuminosilicate glass to a depth of layer, and wherein the compressivelayer comprises a maximum compressive stress of at least about 400 MPaat the surface.

Aspect (63) pertains to the method according to Aspect (62), wherein themaximum compressive stress is at least 800 MPa.

Aspect (64) pertains to the method according to any one of Aspects (62)through (63), wherein the depth of layer comprises at least about 40 μm.

Aspect (65) pertains to the method according to any one of Aspects (62)through (64), wherein the maximum compressive stress is at least 1050MPa.

Aspect (66) pertains to the method according to any one of Aspects (62)through (65), wherein ion exchanging the alkali aluminosilicate glasscomprises immersing the alkali aluminosilicate glass in a molten saltbath.

Aspect (67) pertains to the method according to Aspect (66), wherein themolten salt bath comprises NaNO₃.

Aspect (68) pertains to the method according to Aspect (66), wherein themolten salt bath comprises KNO₃.

Aspect (69) pertains to the method according to Aspect (66), wherein themolten salt bath comprises NaNO₃ and KNO₃.

Aspect (70) pertains to the method according to any one of Aspects (62)through (69), wherein the alkali aluminosilicate glass article has athickness in a range from about 0.05 mm to about 1.5 mm.

Aspect (71) pertains to the method according to any one of Aspects (62)through (70), further comprising joining the ion exchanged alkalialuminosilicate glass to a substrate to form a laminate structure.

Aspect (72) pertains to the method according to any one of Aspects (62)through (70), further comprising joining the ion exchanged alkalialuminosilicate glass to an electronic device housing.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing description should not be deemed to be alimitation on the scope of the disclosure or appended claims.Accordingly, various modifications, adaptations, and alternatives mayoccur to one skilled in the art without departing from the spirit andscope of the present disclosure or appended claims.

1. An alkali aluminosilicate glass article comprising: a thickness t, acompressive stress layer extending from a surface of the alkalialuminosilicate glass to a depth of layer (DOL), and a central regioncomprising a maximum tensile stress, wherein the central region extendsfrom the DOL, and wherein the alkali aluminosilicate glass is free ofB₂O₃ and comprises at least about 58 mol % SiO₂, from about 0.5 mol % toabout 3 mol % P₂O₅, at least about 11 mol % Al₂O₃, Na₂O and, Li₂O,wherein the ratio of the amount of Li₂O (mol %) to Na₂O (mol %)(Li₂O/Na₂O) is less than 1.0, wherein the DOL is less than or equal to0.25*t, and wherein the maximum tensile stress is about 35 MPa orgreater.
 2. The alkali aluminosilicate glass article according to claim1, wherein the glass article further comprises a tensile stress profilein the central region, wherein the tensile stress profile issubstantially parabolic.
 3. The alkali aluminosilicate glass articleaccording to claim 1, wherein the alkali aluminosilicate glass articlecomprises a fictive temperature T_(f) that is equal to a temperature atwhich the alkali aluminosilicate glass article has a viscosity of 10¹¹Poise.
 4. The alkali aluminosilicate glass article according to claim 1,wherein the alkali aluminosilicate glass article comprises a zirconbreakdown temperature of less than about 35 kPoise.
 5. The alkalialuminosilicate glass article according to claim 1, wherein the alkalialuminosilicate glass article comprises a liquidus viscosity of at least200 kPoise.
 6. The alkali aluminosilicate glass article according toclaim 1, wherein the alkali aluminosilicate glass article comprises aratio R₂O (mol %)/Al₂O₃ (mol %) that is less than 2, whereR₂O=Li₂O+Na₂O.
 7. The alkali aluminosilicate glass article according toclaim 1, wherein the alkali aluminosilicate glass article comprises atotal amount of SiO₂ and P₂O₅ that is greater than 65 mol % and lessthan 67 mol % (65 mol %<SiO₂ (mol %)+P₂O₅ (mol %)<67 mol %).
 8. Thealkali aluminosilicate glass article according to claim 1, wherein thealkali aluminosilicate glass article comprises a relationship R₂O (mol%)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol %) that is greater than about −3mol %, wherein R₂O=the total amount of Li₂O and Na₂O present in thealkali aluminosilicate glass article and WO is a total amount ofdivalent metal oxides present in the alkali aluminosilicate glassarticle.
 9. The alkali aluminosilicate glass article according to claim1, wherein the alkali aluminosilicate glass article comprises from about58 mol % to about 65 mol % SiO₂; from about 11 mol % to about 20 mol %Al₂O₃; from about 6 mol % to about 18 mol % Na₂O; from 0 mol % to about6 mol % MgO; and from 0 mol % to about 6 mol % ZnO.
 10. The alkalialuminosilicate glass article according to claim 1, wherein the alkalialuminosilicate glass article comprises P₂O₅ in an amount in a rangefrom about 0.5 mol % to about 2.8 mol %.
 11. The alkali aluminosilicateglass article according to claim 1, wherein the alkali aluminosilicateglass article comprises Li₂O in an amount up to about 10 mol % Li₂O. 12.The alkali aluminosilicate glass article according to claim 1, whereinthe alkali aluminosilicate glass article is free of K₂O.
 13. A method ofmaking a strengthened alkali aluminosilicate glass, the alkalialuminosilicate glass having a compressive stress layer, the methodcomprising: generating a compressive stress in an alkali aluminosilicateglass article by ion exchanging the aluminosilicate glass article,wherein the alkali aluminosilicate is free of B₂O₃ and K₂O and comprisesat least about 58 mol % SiO₂, from about 0.5 mol % to about 3 mol %P₂O₅, at least about 11 mol % Al₂O₃, Na₂O and, Li₂O, wherein the ratioof the amount of Li₂O (mol %) to Na₂O (mol %) (Li₂O/Na₂O) is less than1.0, wherein the compressive stress layer extends from a surface of thealkali aluminosilicate glass to a depth of layer, and wherein thecompressive layer comprises a maximum compressive stress of at leastabout 400 MPa at the surface.
 14. The method according to claim 13,wherein the maximum compressive stress is at least 800 MPa.
 15. Themethod according to claim 13, wherein the depth of layer comprises atleast about 40 μm.
 16. The method according to claim 13, wherein themaximum compressive stress is at least 1050 MPa.
 17. The methodaccording to claim 13, wherein ion exchanging the alkali aluminosilicateglass comprises immersing the alkali aluminosilicate glass in a moltensalt bath.
 18. The method according to claim 17, wherein the molten saltbath comprises NaNO₃.
 19. The method according to claim 17, wherein themolten salt bath comprises KNO₃.
 20. The method according to claim 17,wherein the molten salt bath comprises NaNO₃ and KNO₃.
 21. The methodaccording to claim 13, wherein the alkali aluminosilicate glass articlehas a thickness in a range from about 0.05 mm to about 1.5 mm.
 22. Themethod according to claim 13, further comprising joining the ionexchanged alkali aluminosilicate glass to a substrate to form a laminatestructure.
 23. The method according to claim 13, further comprisingjoining the ion exchanged alkali aluminosilicate glass to an electronicdevice housing.